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A resident of Cady Road petitioned the Agency for Toxic Substances and Disease Registry (ATSDR) to determine if exposure to possible contaminants in private well water and indoor air could adversely affect the health of area residents [1]. This health consultation identifies potential human exposures and possible health effects related to chemicals detected in private well water and indoor and outdoor air sampling data from homes along Cady Road. This health consultation is not intended to be a complete assessment for all environmental risks in the area, nor a study to determine the source of natural gas present in the aquifer.

Residents living on the western half of Cady Road (about 25 homes) have used private well water since the 1950s. The eastern half of Cady Road receives municipal water from the city of Cleveland, Ohio since about the mid -1980s. Residents on the western end of Cady Road that use private well water have complaints about their water quality, mainly the presence of gases and odors in the water (see "Community Concerns" section below). The Ohio Department of Natural Resources (ODNR) has stated that natural oil and gas deposits may impact shallow groundwater due to the unique geology of the area [2]. A fault line intersects Cady Road and has caused a major fracture in the shale underneath the aquifer used for drinking water by private well owners [2,3]. This fracture could allow the migration of underlying oil and gas deposits to upper water-bearing zones [2]. Some residents are concerned that past or present activities from nearby oil and gas extraction wells and a brine (saltwater) injection well in the area have affected their water quality [4-6]. Many of these wells have a history of violations relating to maintenance and accidents [7]. Except for the investigation done by the ODNR (referenced above), other studies or sampling data are not available to determine if the local aquifer has been impacted by oil and gas extraction activities.


Cady Road is in North Royalton, a suburban area about 20 miles southeast of Cleveland, Ohio. The community is mostly residential and consists of the homes (approximately 25 homes or 50 people) that use private well water along the western ½ mile segment of Cady Road. See the map in Appendix A for more information on demographics. Between 1954 and 1958, many of the current oil and gas wells were drilled about 3000 feet deep at varying elevations along Cady Road for oil and gas extraction from geologic reservoirs [2,8]. Currently, there are approximately 8 oil and gas production wells and one former (plugged) saltwater injection well about 1/4 - 1/2 mile from the nearest private water well [8].

The occurrence of natural gas in private well water has been reported since water wells were drilled along Cady Road in the 1950s [2]. Private well water was reported to be cloudy and to "fizz", likely caused by methane (main component of natural gas) "off-gassing" (or bubbling out of the water). Municipal water was provided to half of the homes on the road in the early 1980s. However, there are about 25 homes that still rely on private wells for potable water.

In response to complaints from Cady Road residents, the Ohio Department of Natural Resources (ODNR) took readings of combustible gases (including methane) on a portable handheld instrument on several occasions in 1995 at different homes on Cady Road. These readings measured from below 4% of the lower explosive limit (LEL) at indoor and outdoor taps to 5-8% of the LEL in capped water samples taken from an outdoor wellhead [9]. In addition, hydrogen sulfide measurements in ambient air near outdoor faucets, well houses, and in basements along Cady Road were taken by the ODNR; however, none was detected [10]. Both methane and hydrogen sulfide are gases that bubble out of the water into the air when the water leaves the tap [11].

The lower explosive limit (LEL) is the lowest level of a chemical that would be explosive in air. There is also an upper explosive limit (UEL), which is the highest level of a chemical that is explosive. The range between the LEL and UEL is the 'explosive range'. For methane, the LEL is 5% and the UEL is 15% (i.e., explosive range is 5-15%).In 1995, a Cady Road resident asked the Cuyahoga County Board of Health (CCBH) and ODNR to conduct an investigation to determine if natural gas, oilfield brine (or saltwater), and oil from nearby oil and gas wells were affecting private well water quality. The Ohio Department of Health (ODH) and the ODNR each collected and analyzed one well water sample and found no chemicals at levels of health concern [12,13]. In 1997, the Ohio Environmental Protection Agency collected a sample from a stream near Cady Road because residents had concerns that the oil and gas extraction wells were contaminating surface water in the area. The surface water sample contained no chemicals at levels of health concern [14]. In 1998, the Environmental Protection Agency (EPA) investigated a complaint from a resident of a gas-like odor by collecting indoor and outdoor air grab samples (collected in under one minute) from two homes [15]. The sample results contained several VOCs in indoor and outdoor air. EPA's review of the data indicated that additional sampling was needed [16]. The water and air samples taken previously by these agencies were not analyzed for components of natural gas, such as methane and hydrogen sulfide.

Other than one private well being analyzed for chemical contamination by the ODH and the ODNR over seven years ago, analytical testing data for Cady Road private well water exist for bacteria and chlorides only. Additionally, the ambient air sampling event in 1998 utilized grab samples, which are not representative of long-term exposure, and no pressure gauge which would ensure a fully evacuated canister. For these reasons, ATSDR determined that private well water and ambient air quality of these homes were not adequately characterized to determine whether or not a health threat exists. Therefore, to complete the evaluation of private well water on Cady Road, ATSDR conducted an exposure investigation (May 2002) and included both private well water testing and indoor and outdoor ambient air testing at nine homes on Cady Road. Follow-up sampling was conducted in September 2002 to determine if hydrogen sulfide was present at levels that would pose a chronic health threat.

Community Concerns

Some residents have reported numerous health concerns including dizziness, lightheadedness, passing or blacking out, shortness of breath, fatigue, headaches, metallic taste in mouths, rashes, swelling of legs, elevated blood pressure, flushing of the skin, and muscle spasms [4-6].

Some residents also have concerns regarding their private well water including: gas, rotten egg, and metallic odors emanating from drinking water, saltiness of water, high bacterial counts in water, black-colored water, and an oily feel, look, and taste of the water. Some residents are extremely concerned that their drinking water can be ignited. Others report explosions at their wellheads and gas bubbling up through the ground [4-6].

Some residents also have these concerns: oil and gas activities contaminating the water, water corroding plumbing fixtures, water filters not improving water quality, frequent water filter replacement, an iridescent film in the sink and toilet, "oily" dishes even after washing, and poor water pressure [4-6].

Many residents filter their well water because of the high turbidity and general concerns about water quality, and "shock" chlorinate (dumping household bleach into the well) their well water because of high bacteria (fecal coliform) levels. Some residents use bottled water for drinking, but use tap water for other uses in the home (e.g., showering) [5].

Previous ATSDR Activities

In May 2001, ATSDR conducted a site visit and held a public meeting to collect community concerns. An ATSDR health consultation was released for public comment in September 2001 that evaluated all data collected up to and including 1998. The document concluded that given the available environmental data, the private well water did not pose a public health hazard. However, upon receiving additional information about the site and a number of comments from residents indicating a high level of community concern, an exposure investigation was conducted, and the health consultation was revised and re-released. Public comments received for the health consultation released in September 2001 will not be addressed since this document replaces the September 2001 draft. Public comments to the release of this document have been included in Appendix H.


Private Well Water Results

During the May 2002 exposure investigation, well water from nine homes was collected and analyzed for metals, VOCs, Semi-Volatile Organic Compounds (SVOCs), dissolved gases, sulfides, and inorganic ions. During the water sampling, water treatment systems (owned and installed by homeowners) were bypassed to give a worst-case exposure scenario. Appendix B and C contains additional information on the methods used for the exposure investigation and a quality control and quality assurance (QA/QC) discussion. See Appendix D for the detailed water results. Appendix E lists all of the metals and inorganic ions included in the water analysis.

Metals and Other Inorganic Chemicals

All untreated well water samples contained several metals and inorganic ions commonly found in groundwater. The levels were compared to EPA's Maximum Contaminant Levels (MCLs) and Secondary Maximum Contaminant Levels (SMCLs) and ATSDR's health-based comparison values (CVs), as shown in Table 1 below.

Table 1. Metals and Inorganic Ions Detected in Drinking Water

  Result Range* EPA MCL† EPA SMCL‡ ATSDR CV§
Aluminum 28–1,700 None 50 20,000
Barium 17–160 2,000 None 700
Calcium 3,200–7,700 None None None
Chromium 2.7–6.5 100 None 100
Copper 8.9–37 None 1,000 1,300
Iron 66–12,000 None 300 None
Lead 20 15 None 15
Magnesium 1,700–3,200 None None None
Manganese 7–60 None 50 500
Molybdenum 21–24 40 None 50
Potassium 1,300–2,900 None None None
Sodium 160,000–330,000 None 20,000¶ None
Zinc 3.5–560 None 5,000 2,000
Inorganic Ions
Bromide 510–790 None None None
Chloride 94,000–160,000 None 250,000 None
Fluoride 1,400–1,800 4,000 None None
Nitrate 5.8–8.1 10,000 None 10,000
Sulfate 130–44,000 None 250,000 None

*All results are in parts per billion (ppb).
†MCL: Maximum Contaminant Level.
‡SMCL: Secondary Maximum Contaminant Level.
§CV: Comparison Value.
¶EPA's Drinking Water Equivalent Level (DWEL).

All of the inorganic ions and metals detected were below health-based comparison values, with the exception of sodium (9 wells) and lead (1 well). All of the wells had fairly saline (salty) water with sodium as high as 330,000 ppb (parts per billion or micrograms per liter) and chloride as high as 160,000 ppb. Lead was found in one well at 20 ppb, a level slightly above EPA's MCL for drinking water and above the ATSDR CV of 15 ppb. The source of the lead is unknown. Since it was found in one sample only at low levels, ATSDR contacted the homeowner about the results and recommended that the test be repeated.

EPA's SMCLs were slightly exceeded for aluminum (in 2 wells), iron (in 4 wells), and manganese (in 1 well). The SMCLs are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration at very high levels) in residents or aesthetic effects (such as taste, odor, or color) in drinking water, but are not expected to cause health effects in humans. The metals detected in groundwater were similar from home to home on the western end of Cady Road and may be inherent in the shallow aquifer, reflecting natural geology. The easternmost well had higher levels of aluminum (1,700 ppb), iron (12,000 ppb), sodium (330,000 ppb), and zinc (560 ppb). It is unknown why this location had a higher level of metals. Since the water samples were not filtered prior to analysis, it is possible some of these metals were due to small amount of silt or sediment within the water. Certain water filtration systems will help to reduce the level of metals attached to this silt or sediment in drinking water. See the section "Public Health Implications" and Appendix F for an evaluation of metals in drinking water.

Volatile Organic Compounds and Dissolved Gases

All of the well water samples exhibited entrained (trapped) gases at the time of sampling. The sampled water was often milky, bubbling, and actively releasing dissolved gases while running the water at even very low flow rates to limit turbulence. Since gases escaped from the water during sampling and transport, the laboratory analysis can only provide low estimates of these gases in the water at the point where the water comes out of the faucet. Gases that readily leave the water (volatile gases) are not easily quantified under these sampling conditions. Therefore, all results reported (or otherwise not listed in the tables) for VOCs and dissolved gases should be considered underestimates. A gas or VOC not detected during laboratory analysis may have been present at low levels in the water, but was reduced during sampling and transport.

The water samples indicate the presence of dissolved gases consistent with oil and gas deposits, such as methane in all the wells (1 ppm (part per million) to 11 ppm) and sulfides in two wells (1.8 ppm and 4.2 ppm). The detection limit for sulfides is 1 ppm; therefore, sulfides may be present in other water wells at levels less than 1 ppm. Other VOC and SVOC compounds consistent with gas deposits identified include ethane, ethene, propane, butane, isobutene, 2-methylbutane, and pentane. A few samples contained acetone (three wells) and methylene chloride (four wells) in low levels, below health guidance values. The source of these contaminants is unknown, but acetone and methylene chloride are common laboratory contaminants. See Appendix D, Table 2, for more detailed water results.

The purpose of water sampling for dissolved gas analyses was primarily to confirm the presence of the gases in the water. The levels detected may not represent the amount of gases one would be exposed to when drinking the water because some of the gas could escape into the air. To determine how much of the escaped or volatilized gas people could be breathing, 8-hour time-weighted-average (TWA) air samples were collected inside homes.

Indoor and Ambient Air Results

The presence of dissolved gases and sulfides (most likely hydrogen sulfide) in the water indicates that these compounds may also be in indoor air. As described previously, the gases were observed bubbling out of the water during sampling. The highest air concentrations of these compounds would be expected during heavy water usage. Therefore, ATSDR conducted air screening during the flushing of the water systems and air sampling with canisters to record the levels of the gases.

Hand-held air screening instruments were used to give real time concentrations of methane (and other combustible gases) and hydrogen sulfide. The monitoring took place in basements while wells were being flushed for water sampling, as well as bathrooms or other living areas, and outdoors near wellheads. ATSDR used a flame ionization detector (FID) to measure total VOCs, including methane, in the basement, while a photo-ionization detector (PID) was used to measure other total volatiles (except methane) that were off-gassing from the water as water samples were collected. A multi-gas meter was used during sampling to monitor explosive atmosphere conditions (%LEL), oxygen levels (%), carbon monoxide, and hydrogen sulfide in the ppm range. Air was collected over an 8 hour period, from selected indoor and outdoor areas, by slowly filling a metal canister (SUMMA® canisters). These samples were analyzed by the laboratory for gases and VOCs. See Appendix B and C for more information on methods of air sampling used during the exposure investigation.

Air Screening Results

During ATSDR's investigation, the sampling team heard bubbling of gases in two wells from several feet away. The screening instruments detected explosive levels of combustible gases in ambient air near these two residential wellheads. Additionally, while flushing the water system in basements (for approximately 20 minutes), combustible gas levels increased from 0 to 9% (about 5,000 ppm) and from 0 to over 19% (about 11,000 ppm) of the lower explosive limit (LEL) in two of the homes. An additional 4 homes had FID readings above 1,000 parts per million (2% of the LEL) while running the water. In fact, FID readings in all homes increased while running water, suggesting that well water is the source of combustible gases in the homes sampled.

ATSDR also performed air screening before the treatment systems were bypassed upon initial entry of the home. Because screening instruments also detected combustible gases in treated tap water, this indicated that the water treatment systems in the homes do not eliminate the release of gases into ambient air.

The elevated gases detected in homes during real-time monitoring appeared to be mostly methane and other (natural gas) associated compounds. The source appears to be the water since levels increased while running tap water and decreased when the water was no longer in use. The FID (which detects methane and other VOCs) showed peak levels near the running water while the PID (which detects VOCs but not methane) showed extremely low levels or no VOCs. Methane was also the gas detected at higher concentrations than any other combustible gases in the laboratory analysis of air and water samples.

A hydrogen sulfide odor was observed at many homes on Cady Road. Screening values indicated that hydrogen sulfide was present at one household at 28 ppm in the basement near the sink where water was being flushed, and at 5 ppm in the same basement away from the sink. A different household had hydrogen sulfide levels at 9 ppm by the wellhead.

Air Analytical Results

ATSDR used a time weighted average sample to be representative of exposure throughout the day.

Gases - In general, 8-hour SUMMA® canister samples did not demonstrate the same elevations of combustible gases as the screening instruments. SUMMA® samples represent a time weighted average over 8 hours, so the short term peak concentrations observed during water usage are diluted by the air that is present when water is not used. Methane was detected at low levels in all indoor samples, except one, which was collected in a basement utility shelter more than 15 ft from the tap being sampled. No hydrogen sulfide was detected in any of the 8-hour indoor air samples. This may be in part due to the canister valving that was designed for VOC collection and analysis. No methane or associated (natural gas) chemicals were detected in any of the three 8-hour ambient air samples collected in yards. These data indicate that average air contaminant levels are low, and that gases are quickly diluted in air after water usage. One grab air sample was taken at one of the wellheads where screening instruments detected explosive levels. This sample contained 300,000 ppm methane (equal to 30% methane which is over the explosive range of 5-15%) and other associated gases and 7.3 ppm hydrogen sulfide.

VOCs - Low levels of commonly occurring chemicals in indoor and outdoor air, including those that are components of fuels, were detected in the 8-hour time weighted average samples. The results indicate that average levels are low, which suggests that any VOCs present in the air from water dissipate rapidly in the homes after water usage. The results of the laboratory analysis of the SUMMA® (8-hour) samples were compared to health guidance values. All of the chemicals detected were below health guidance values, with the exception of benzene, which ranged from 0.2 ppb to 5.6 ppb. Health effects of benzene are discussed in the "Public Health Implications" section. See Appendix D for detailed results of the laboratory analysis for VOCs.

Hydrogen Sulfide Follow-up Sampling

During the May 2002 sampling event, ATSDR detected hydrogen sulfide in high levels while running the water in a few homes. The detection limit of the instrument used for hydrogen sulfide was about 1,000 ppb in the initial air sampling. In order to determine if residents were being chronically exposed to low levels of hydrogen sulfide, ATSDR performed additional air screening at the two homes where high levels were detected previously and one home where odors were previously observed.

ATSDR detected hydrogen sulfide at levels of only 1-2 ppb in the home where it was only previously detected by odor. This level is not high enough to pose a chronic health concern. In the two homes where hydrogen sulfide was previously detected, ATSDR found levels of 100 ppb (home 1) and 40 ppb (home 2) in the living areas before any water was turned on. ATSDR simulated a shower scenario by running the water in the bathroom with a closed door for 10-15 minutes. The shower scenario at home 1 resulted in hydrogen sulfide levels of 10,000 ppb after about 10 minutes of running the water, and 18,000 ppb after about 15 minutes. At home 2, just turning the kitchen faucet on immediately increased the level of hydrogen sulfide to above 50,000 ppb. Running water at this home during a shower scenario gave consistent readings between 40,000 and 60,000 ppb.

Recreational Water Results

ATSDR sampled a pond and well located in an area on Cady Road that the Boy Scouts actively use. The pond and well were sampled during the exposure investigation because of community concerns about pollution from oil and gas activities [5]. Visual observations of the pond indicated an oily sheen on the surface. The pond sample was analyzed for total oil and grease, metals, and inorganic ions. The sample was not analyzed for dissolved gases or VOCs since these compounds would readily volatilize from the pond. Metals or inorganic ions were not detected at levels that would cause a health concern for recreational use of the pond. Sodium (32,000 ppb) and chlorides (76,000 ppb) were lower in the pond sample than any of the private well water samples. Oil and grease were detected in very low levels and indicates that the pond has not been significantly impacted by petroleum products at the time of sampling.

The nearby well is operated by a hand pump, and is only used by the Boy Scouts during camping. The hand-pump well sample was analyzed for the same contaminants as other private water wells on Cady Road. No gases were detected in air by screening instruments or dissolved in water by laboratory analysis. The levels of metals detected were below health guidance values. Levels of nitrates (1,100 ppb) and sulfates (12,000 ppb) were higher than the other private water well results, but still below EPA's MCLs and SMCLs. The results for the pond and hand-pumped well were below health screening values, and will not cause any adverse health effects.

Exposure Pathways Analysis

ATSDR examined the possible exposure pathways and determined that inhalation and ingestion are the primary pathways of concern. Some residents are exposed via ingestion by drinking either the treated or untreated tap water. All residents are exposed via inhalation by using the treated or untreated water for other domestic uses besides drinking, such as cooking and bathing. A physical hazard pathway is also present due to the potential for explosive levels of gases to build up in homes.

Public Health Implications

The metals and inorganic ions in the well water samples are not a health hazard. The majority are below EPA's established MCLs and SMCLs. For those metals without MCLs, ATSDR compared recommended daily values of a healthy diet to the measured concentrations of metals. These metals were below recommended daily values and are discussed in more detail in Appendix F. However, the sodium chloride levels are higher than desirable and people who have elevated blood pressure or who are on a sodium-restricted diet should minimize their consumption of the water or treat the water to reduce the level of sodium.

Dissolved gases in the drinking water are the greatest concern. Although none of the gases or organic compounds measured in the drinking water pose an ingestion hazard, the gases released to air may pose an inhalation hazard. This is an important point as overall water usage, especially gas levels during periods of high water usage (such as showering), may result in high levels of explosive gases or hydrogen sulfide in the air. This release is not prevented by the use of bottled water for drinking and food preparation.

The types of hydrocarbons which make up natural gas (e.g., alkanes such as methane, ethane, and pentane) generally pose a hazard only if there are levels high enough to be an explosion hazard or asphyxiation hazard by creating low oxygen levels. Hydrogen sulfide is often found in natural gas deposits and has health effects at high levels. Benzene, found in a few homes, is a known human carcinogen. Therefore, the discussion of public health implications focuses on the detected levels of methane, hydrogen sulfide, and benzene in the air.


Methane is a naturally occurring, flammable gas made of carbon and hydrogen that forms explosive mixtures with air; the flammable range for methane concentrations in air is 5% to 15 % by volume [17]. This means that the lower explosive limit (LEL) is 5% and the upper explosive limit (UEL) is 15%. Methane levels below 5% by volume in air and above 15% by volume in air are not explosive. It is odorless, tasteless, and is primarily used as fuel. Methane can be released to the environment via the manufacture, use, and disposal of many products associated with petroleum and gasoline industries. Methane is also a byproduct of decomposition. It may also be released to the environment as emissions from coal off-gassing, combustion, and liquefaction [18]. As a natural gas, methane generally occurs with other hydrocarbons as well as carbon dioxide, nitrogen, and sulfur compounds (such as hydrogen sulfide). "Sour" natural gas typically contains 5 percent hydrogen sulfide, which makes it somewhat corrosive [19-21].

During the exposure investigation, explosive levels of methane and other combustible gases were detected near the openings of wellheads at two homes on Cady Road. In addition, 9% of the LEL at one home and 19% of the LEL at another home were found in the basements during water sample collection. At these levels, EPA recommends that the area be monitored with extreme caution. If the level reaches 25% of the LEL (or 1.25% methane by volume of air), the area is considered to be an explosion hazard and should be evacuated immediately [22].

The source of the methane is the well water. Although gases generally dissipate quickly in ventilated rooms upon cessation of running water, they may buildup in enclosed spaces, posing a fire and explosion hazard. If there is a source of fire or ignition in these spaces, such as a spark, this could cause the built-up gases to catch fire or explode. There have been reports of two well pumps on Cady Road exploding and other residents have reported the ability to ignite the water [5,6]. Although not all homes sampled on Cady Road had high levels of combustible gases in their homes during the exposure investigation, it is unknown how levels of gases fluctuate with differing water usages, seasons, temperature, and other factors. The exposure investigation only captured the conditions of one day out of the year. Because the source of the gases in the home is the well water, and all wells tap into the same aquifer (Berea sandstone aquifer) [2], this assessment of combustible gases applies to all homes on Cady Road that have a private well and use the well water for any reason.

Most wellheads at the homes sampled had caps that prevented ATSDR from using screening instruments to detect gases coming from the wellhead. One well did not have a cap, since in previous instances the cap would "blow off" from the pressure of the built-up gases.

Venting wellheads can reduce combustible gas concentrations in the well water coming through the tap. Proper venting will allow the gases to escape but also prevent any contamination from entering the well and impacting water quality. Removing the well cap is not an appropriate method of venting these wells. Debris, insects, and even small animals may fall into the well, resulting in water quality issues including bacterial contamination. Proper venting of a wellhead should be completed by a professional. Note that venting the wellhead will not completely remove methane and other dissolved gases from the well water, but ventilating will eliminate a pressure buildup of methane in the well. Elevated levels of dissolved gases, including methane, were found in well water from a Cady Road well which had the cap removed for venting.

Methane is also a simple asphyxiant (at around 87% by volume). Simple asphyxiants displace oxygen from the breathing atmosphere primarily in enclosed spaces and can result in hypoxemia, or insufficient oxygen in the blood [23]. Exposure to methane can produce symptoms of central nervous system depression including nausea, headache, dizziness, confusion, fatigue, weakness, and loss of coordination and judgment [24-26]. Residents have reported many of these symptoms. Although methane has practically no clinical effects at concentrations less than the Upper Explosive Limit (UEL), two wells had levels of methane above the UEL near the wellhead. If these levels of gases were to build up in enclosed areas, they could displace oxygen to a dangerous level. The air screening instruments in one home showed a decrease in the level of oxygen to 18.2%. This infers that residents could potentially experience these effects due to buildup of methane and other combustible gas levels in enclosed areas in the home.

The combustible gas levels measured through screening and analytical methods at homes along Cady Road are a physical hazard. Levels of gases were detected within the explosive range or above at two wellheads, and near explosive levels in two basements. A risk of fire and explosion exists for any enclosed area in which private well water is used. Residents could also experience potential non-life threatening effects from the levels of methane and other combustible gases detected in their water wells, including dizziness, headaches, nausea, and fatigue. Methane and other combustible gases pose an urgent public health hazard to Cady Road area residents that have private well water. An alternate water source would eliminate this hazard.

Hydrogen Sulfide

Hydrogen sulfide is a colorless, flammable gas under normal conditions. Hydrogen sulfide gas in water usually does not pose a health risk, but gives the water a nuisance "rotten egg" smell and taste. People can smell hydrogen sulfide as low as 0.5 ppb. It is found naturally as a constituent of crude petroleum, natural gas, volcanic gases, and is often the result of bacterial breakdown of organic matter. Industrial sources of hydrogen sulfide include petroleum refineries and natural gas plants. Hydrogen sulfide is also produced in the human body in the mouth and gastrointestinal tract [27].

Hydrogen sulfide is a gas formed by sulfur bacteria that may occur naturally in water. These bacteria use the sulfur in decaying plants, rocks, or soil to produce hydrogen sulfide as a by-product. Geologic deposits of sulfur are usually in the same places as oil and gas deposits in Ohio as well as in coal deposits [28]. The sulfur bacteria do not cause disease, but their presence in water can cause a bad taste or odor.

Dissolved hydrogen sulfide in water can corrode plumbing as well as exposed metal parts in washing machines or other water-using appliances. Iron and steel corrosion from hydrogen sulfide forms ferrous sulfide or "black water" which can darken silverware and discolor copper and brass utensils [29]. Hydrogen sulfide in air can also discolor copper. Hydrogen sulfide can also interfere with the effectiveness of water softeners.

High water usage in an enclosed environment may result in short term exposures to hydrogen sulfide in levels greater than 1,000 ppb as demonstrated by data collected during the initial investigation. Flushing water pipes for 15 to 20 minutes resulted in measurable hydrogen sulfide as high as 28,000 ppb. The follow-up air screening that utilized a shower scenario resulted in levels of hydrogen sulfide up to 18,000 ppb and 60,000 ppb in two homes.

Short term exposures to high levels of hydrogen sulfide may cause adverse health effects. For example, bronchial constriction was noted in 2 out of 10 asthmatics exposed to 2,000 ppb hydrogen sulfide for 30 minutes [30]. Other studies have documented respiratory distress in an occupational setting with exposures of greater than 40,000 ppb hydrogen sulfide, and changes in oxygen uptake, and shortness of breath in subjects exposed to between 5,000 and 10,000 ppb hydrogen sulfide for short periods of time [31-35]. The data suggest that residents could be intermittently exposed to levels of hydrogen sulfide that could result in these types of effects. Much higher levels of hydrogen sulfide may result in loss of consciousness and respiratory distress or possibly death (greater than 500,000 ppb) [27].

Long term exposures to high levels of hydrogen sulfide may also cause adverse health effects. For example, neurological effects resulting from chronic (long-term) exposure to hydrogen sulfide in the shale industry have been reported. Symptoms in workers exposed to daily concentrations of hydrogen sulfide (which often exceeded 20,000 ppb) included fatigue, loss of appetite, headache, irritability, poor memory, and dizziness [36]. In addition, prolonged exposure to high levels of hydrogen sulfide can cause the person to no longer be able to smell the gas. Therefore, the person would not be aware of increasing hydrogen sulfide levels [27]. Hydrogen sulfide in the two homes that had measurable levels of 60,000 ppb may result in adverse health effects.

The hydrogen sulfide released during water usage in the homes may also contribute to low level (<1,000 ppb) long term exposures to hydrogen sulfide. These health effects are not well known. A recent study examining health effects in a community exposed to low levels of hydrogen sulfide noted an increase in asthma-related hospital visits among children following days when H2S levels are above 30 ppb [37]. Several studies of communities exposed to low levels of malodorous sulfur compounds (including hydrogen sulfide, methyl mercaptan and methyl sulfides) indicate an increase in reported nasal symptoms, coughs and breathlessness or wheezing with increasing air concentrations of these compounds [27]. However, it is not known if these symptoms can be attributed solely to hydrogen sulfide, since other compounds existed as well. If there are persistent low levels of hydrogen sulfide in the homes, some of these health effects may be possible.

The hydrogen sulfide levels detected during screening and laboratory analysis indicate that adverse health effects could result from intermittent or chronic exposures. This is a particular concern for residents with pre-existing conditions such as asthma or respiratory problems. Hydrogen sulfide in water is a public health hazard to residents on Cady Road that use private well water. The follow-up screening using a shower scenario indicated that hydrogen sulfide levels in two homes are more of a serious concern than in the homes previously sampled. An alternate water source would eliminate this hazard.


Benzene is a colorless, flammable liquid with a sweet odor that evaporates readily into air and dissolves slightly in water. Benzene cannot be smelled in air until it reaches about 1.5 - 4.7 ppm (1,500 - 4,700 ppb) and cannot be smelled in water until it reaches about 2 ppm (2,000 ppb). Benzene is found naturally as a component of crude oil and gasoline, and used for the manufacturing of many products. Sources of benzene in air include burning coal and oil, motor vehicle exhaust, gasoline vapors, cigarette smoke, and storing vehicles, lawn mowers, etc. in attached garages [38].

Indoor air levels of benzene ranged from 0.2 ppb to 5.6 ppb (see Appendix D) in the homes sampled on Cady Road. Since the analysis of VOCs in water may have underestimated the levels (see the private water results section), it is unknown if the source of benzene in the air is the water or other sources in the home. There are many sources of benzene inside the home, including cigarette smoke, gasoline or fumes from an attached garage, and products such as glues, paints, waxes and detergents. However, benzene was detected in the grab air sample taken from a wellhead (0.2 ppb), which suggests that it may be a component of gas in the water.

If the levels of benzene measured in the air samples represent long-term conditions in the home, standard risk calculations demonstrate that the levels of benzene may indicate a marginal increase in cancer risk. However, the meta-analysis (analysis of multiple studies) of human epidemiological studies shows that benzene exposure does not result in cancer in workers until levels of benzene reach about 20,000 ppb in air [38]. In addition, background levels of benzene in ambient air range from 2.8 to 20 ppb and it is common to find elevated levels of benzene inside homes due to indoor sources [39]. The levels of benzene measured in the homes are not a public health hazard. Any sources of volatile organic chemicals should always be stored in areas away from the living quarters (such as in a detached garage or shed) to lower exposure to VOCs. Examples of VOCs that should be stored away from the living quarters include gasoline, oil, paints, glues, varnishes, etc.

Childhood Health Initiative

ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of environmental media. Hydrogen sulfide may be a particular concern for children because it may aggravate asthma attacks or allergies or other pre-existing respiratory conditions. The levels of hydrogen sulfide measured during sampling may cause these adverse health effects, and therefore poses a public health hazard to children.

Review of Community Concerns

The community concerns listed under the "Statement of Issues and Background" section are summarized below with respect to their relevance to the contaminants discussed in this document.

  • Exposure to combustible gases such as methane could account for the following community concerns: dizziness, lightheadedness, passing or blacking out, and headaches. Exposure to combustible gases could account for the following water quality concerns: fizzy/gassy, explosions at wellheads, gas bubbling up through the ground, ignitable water.
  • Exposure to hydrogen sulfide could account for the following health concerns: dizziness, lightheadedness, shortness of breath, fatigue. Hydrogen sulfide in the water supply could account for the following water quality concerns: rotten egg odor, black-colored water, water corroding plumbing fixtures, frequent filter replacement.
  • Saltiness is most likely due to high levels of chloride and/or sodium in the water.
  • High bacterial counts in the water may indicate a problem with septic systems.
  • Poor water pressure is likely to be a factor of rainfall and weather conditions, not chemical contamination.
  • An oily feel, look and taste of water, an iridescent film in sink, and "oily" dishes after washing suggest oil contamination; however, this was not observed during the exposure investigation, and results of sampling indicated that water was not impacted by oil contamination.
  • High levels of metals in the water (common for groundwater) may account for the concern about a metallic taste in the mouth and metallic odors from water.
  • High levels of sodium in the water may account for elevated blood pressure if the water is ingested regularly.
  • Community concerns that ATSDR can not directly account for with the current literature on combustible gases and hydrogen sulfide are: rashes, swelling of legs, flushing of skin, and muscle spasms.

Additional Discussion of Community Concerns

The presence of methane and hydrogen sulfide in groundwater is not a unique finding and has been well known in this area and other parts of Ohio for some time. What are unique to the area investigated are the levels of these chemicals found in indoor air, especially during water usage in the home. Community concerns about water quality have focused on the rotten egg smell with some residents noting an ability to light the gases coming out of the water. This may be done from running water or water in a container. Although it would seem water of this quality would be undesirable to residents for a number of reasons, there have been a number of questions raised regarding the exposure investigation sampling and the conclusions that were reached. A few of these broad questions are addressed below to put the report findings in perspective and to further support the conclusions and recommendations in the next section.

1. Why did our sampling find conditions not previously seen?

Prior to ATSDR's involvement, several agencies responded to water complaints on Cady Road and worked to answer the concerns of residents in the area. ATSDR's report builds on these earlier efforts by adding exposure monitoring for combustible gases and hydrogen sulfide in homes on Cady Road, which were not previously done. ATSDR's primary focus was on measuring actual exposure of residents to the chemicals in their private wells. Therefore, ATSDR focused on chemicals associated with natural gas and with sampling in conditions that would represent exposure.

These dissolved gases were demonstrated to be present in the water entering the homes. These chemicals were detected in indoor air and greatly increased with water usage, linking their presence in the water wells to indoor conditions.

Air samples were collected in two ways. One set of samples, collected in canisters, were collected over a long period of time to represent average conditions in the homes. Another set of samples was obtained from handheld instruments that screened air quality while the water was running in each home to represent how someone may be exposed while using the water. This is a very important point since the chemicals we found in the air came from the water. Neither of these air sampling methods have been used in the past in evaluating homes on Cady Road. Although the average air concentrations are not a health concern, the real time monitoring did reveal a hazard. By measuring these gases during water usage, we were able to define a health hazard in some of these homes.

2. How can ATSDR define an explosive hazard, and call it urgent, when the minimum explosive level was not seen in indoor air?

ATSDR considers safety hazards and health hazards an urgent public health hazard if that health effect occurs after short term exposure (i.e., less than one year) (see Appendix G). Air monitoring demonstrated that explosive gases rapidly enter the home through well water at levels which approached 25% of the explosive range. These readings were taken in open areas often in the breathing zone, or the area where a resident would be working over a sink. These readings document a potential for explosive levels to be present in homes. Since conditions in the shallow aquifer may change over time, and conditions in the home may change, it is prudent to protect against this potential. Additionally, water usage in a confined area, or a water leak into a confined area, would be of particular concern for developing an explosive environment. Therefore, these data alone are sufficient to consider these conditions an urgent public health hazard. Flammable conditions in the home were attested to by several residents. One resident can turn on the kitchen faucet and throw in a match creating flames (as demonstrated on the local news). Another resident stated that a burning candle flashed a flame in the bathroom during normal water use. There are two wells which "blow off their well caps" and at least one fire in a pump house. These demonstrations of flammability, along with anecdotal stories going back for some time, taken together with conditions measured in the homes, strongly support the designation of urgent public health hazard.

3. Is my treatment system adequate?

Bottled Water: Many residents indicated they used bottled water for food preparation and drinking water. However, since dissolved gases are the main contaminant of concern the use of bottled water does not eliminate the hazard. Dissolved gases will evolve from water used in the home during cleaning, showering and other activities. These gases may pose a potential explosion hazard and inhalation hazard (hydrogen sulfide) even when not used for drinking water. The use of bottled drinking water will eliminate any concerns the residents have from increased sodium intake or other chemicals from the wells.

Particulate filters (found in 7 out of 10 homes): Rope filters and other particulate filters are designed to remove silt, sediment and other particulates from the well water as it passes through the filter. This treatment technology physically filters and removes particles based on size. Dissolved gases such as methane and hydrogen sulfide are not removed through this type of physical filtration. Therefore the use of a particulate filter will not protect against the dissolved gases.

Carbon Adsorption (found in 5 out of 10 homes): Carbon adsorption is designed to remove dissolved organic chemicals from water. The unit may look similar to a particulate filter, but it is filled with granular activated carbon. Water runs across the activated carbon media and some chemicals stick (adsorb) onto the carbon removing them from the water. This technology is more effective for high molecular weight non-polar compounds [40]. As such it is not efficient for dissolved methane and hydrogen sulfide, although low levels of these chemicals would be removed. Since the activated carbon has limited ability to remove these materials, the hydrogen sulfide would pass through to the user. Carbon adsorption would not be a treatment method of choice for these dissolved gases. Combustible gases were seen in the homes which had carbon adsorption units installed, when water was run in the kitchen, bathroom and basement areas. None of the compounds identified in the exposure investigation suggest a need for carbon adsorption treatment.

Reverse Osmosis (found in 2 out of 10 homes): Reverse osmosis (RO) is a technology primarily used for demineralization and desalination of water. RO may remove other dissolved organic and inorganic chemicals. The efficiency of any RO system in removing a specific chemical will depend upon the design of that system. An RO system designed to address mineral content of the groundwater should not be relied upon to address other chemicals unless it has been designed to do so. Combustible gases were seen in the two homes which had RO systems, when water was run in the kitchen, bathroom and basement areas.

Chlorination (found in 1 out of 10 homes): Chlorination is primarily used to address bacterial contamination in water systems. However free chlorine added to water will also chemically react with hydrogen sulfide and change it into sulfate, resulting in a yellow precipitate. This removes the dissolved gas from the water mitigating any potential inhalation hazard. As with other treatment technologies, it would need to be properly designed and operated to ensure it addressed high levels of hydrogen sulfide, providing enough chlorine and appropriate contact time to be effective. If there is a break in chlorine injection, there would be no treatment and hydrogen sulfide would again be entering the home. Methane is not effectively treated with chlorine.

Aeration (found in 1 out of 10 homes): Aeration of the well water is an appropriate treatment technique for dissolved gasses. These gases, such as methane and hydrogen sulfide, exist under pressure in the aquifer and within the water pipes. When the water leaves the pipes the gases readily escape into the air. Therefore, aeration before use of the water in the homes will reduce the methane and hydrogen sulfide entering the home. When dissolved gases are present at lower nuisance levels, passive aeration, as employed in at least one home on Cady Road, may be adequate. However, higher levels of gases require more aggressive treatment. It should be noted that hydrogen sulfide and explosive gases were detected in this home, even after water treatment. Even when these gases were only present at moderate levels in the well, the passive treatment system did not remove all of the dissolved gases. More aggressive aeration would involve spraying the water, or bubbling air or carbon dioxide through a well ventilated tank. These systems need to be designed for a specific operation, and should be tested to ensure proper treatment is achieved.

4. Why is a new water supply a better answer than household treatment systems?

Residents have voiced concerns regarding the preference for using treatment systems over obtaining an alternate water supply as a solution to removing the gases in the water. The majority of the treatment systems ATSDR observed during sampling are not able to address the dissolved gases found in the drinking water wells. Aeration is an adequate and the preferred treatment for these dissolved gases. However, passive aeration, as seen in one home on Cady Road, may not be adequate for the elevated levels of dissolved gases, as discussed above. More aggressive aeration systems which involve spraying the water into a tank, or bubbling air or carbon dioxide through a well ventilated tank, need to be designed for a specific operation, and should be tested to ensure proper treatment is achieved.

The use of home treatment systems for complex water quality problems is not a preferred solution. Treatment systems for complex water quality problems, as seen on Cady Road may be costly and would have to be designed and tested for the elevated levels of dissolved gases. The level of dissolved gases in some homes is beyond the ability of simple solutions, such as wellhead venting or passive aeration. Additionally, the health hazard due to these gases is an acute hazard. If the system is turned off, bypassed or ceases to operate for any reason, gases would readily enter the home and begin to accumulate. An explosive hazard or hazardous levels of hydrogen sulfide may be encountered if an alternative water supply is not available. The preferred engineering solution that is the most protective of public health is to provide a reliable source of clean water to the residents, and use water treatment systems as an interim measure until a different water source is available. Supplying these homes with a clean and reliable water source should also resolve the controversy about water quality on this road, benefiting all residents. The following bullets summarize the reasons that treatment systems are not encouraged as a long-term solution to the problem of gases in the well water:

  • Due to the unusual level of gases and the potential for variability, individual treatment systems would be difficult to install and manage, allowing for the potential of future exposures.
    • - Each home would have to be evaluated by a professional to determine the correct treatment.
      - It is unknown how levels of gases fluctuate, and if the treatment system would be able to handle fluctuations.
      - Sampling after the treatment system is installed would have to be performed to ensure its efficacy.
  • Treatment systems would have to be continuously maintained in order to be protective, and effective at eliminating or reducing the gases.
  • Residents would not know if gases (which are odorless) reached a level that poses an explosion or fire risk, if the treatment system malfunctioned, without continuous monitoring.


Some homes along Cady Road are impacted by combustible gases and hydrogen sulfide in the drinking water. Residential exposure is through the use of the water for drinking, bathing, and other household uses. ATSDR concludes that:

  • Combustible gases, including methane, in the private well water present an urgent public health hazard. The levels of gases measured near two outdoor wellheads were at explosive levels. These levels could also build up in enclosed spaces, posing a fire and explosion hazard indoors. The urgent public health hazard focuses on homes where high levels of methane were found; however, the extent of these dissolved gases in groundwater is unknown (i.e., how many homes are affected).

  • Hydrogen sulfide in the private well water on Cady Road presents a public health hazard. The levels measured in some homes on Cady Road could cause adverse health effects, especially in residents with a pre-existing condition such as asthma or other respiratory conditions.

  • The levels of sodium measured in the water may be harmful to residents with elevated blood pressure or to residents that require a sodium-restricted diet.

  • The gases and organic compounds measured in the drinking water are not an ingestion hazard.

  • Benzene and other VOCs in indoor air at the levels measured are not a public health hazard.

  • Other than sodium, the metals and inorganic ions levels measured in water are not of health concern.

  • The pond water and water from the hand-pumped well located near the Boy Scout campsite are not of health concern.


  • Provide an alternate whole-house water supply to the remaining homes on Cady Road that do not currently have access to municipal water. The use of bottled water does not negate the explosion and fire hazard associated with the use of well water.

  • Determine the extent of the problem of gases in groundwater (geographically) since sampling was limited to volunteer residents on Cady Road.

  • Until an alternate water supply is available, residents should have a treatment system installed by a professional to decrease the concentrations of gases in the water that is entering the home. A list of water treatment companies certified by the Ohio Department of Health is available by calling 614-466-1390 or on their website at:

Until an alternate water supply is available, these recommendations, based on best public health practice, are considered prudent measures to decrease the risk of fire and explosion:

  • Ventilate well houses to avoid accumulation of combustible gases.

  • Ventilate to the outdoors any enclosed area in the house where water is used (e.g., basements, bathrooms).

  • Avoid all sources of ignition in any enclosed areas (e.g., basements and closets) or other areas identified to have high concentrations of methane or other combustible gases (e.g., near wellheads). Sources of ignition include: pilot lights, lighters, matches, candles, lighting cigarettes or smoking, outdoor grilling or barbecuing, using gas or electric powered equipment, or hammering metal objects that could cause a spark.

  • Consider installing combustible gas indicators in basements or other enclosed areas where running water could result in buildup of gases. The indicator would provide a warning if gases reached near-explosive levels.

  • Consider installing a mechanism on well pumps to ventilate the headspace of the water well. Do not attempt to ventilate the well headspace without professional assistance.

  • Do not completely remove the well cap from the well. An uncapped drinking water well poses a public health hazard since the drinking water is vulnerable to contaminants such as debris and bacteria.

The following recommendation is based on practices observed on Cady Road during ATSDR's exposure investigation, and follows best public health practices:

  • Shock chlorination (dumping household bleach into the well) should only be used as a short-term solution to a bacteria problem. The source of the problem should be determined any time bacteria are detected in a well to prevent reoccurrence. If the source is not determined, the water should be frequently tested for bacteria (e.g., every few months).


Actions Completed

  • In May 2001, ATSDR visited the site and met with residents to collect community concerns.
  • In May 2002, ATSDR conducted an exposure investigation of nine Cady Road homes, and met with and interviewed residents.
  • In June 2002, ATSDR distributed a fact sheet to residents and local, state, and federal agencies concerning the levels of combustible gases found in several homes during the exposure investigation.
  • In June - August 2002, ATSDR discussed the results of the exposure investigation with the Cuyahoga County Board of Health, the City of North Royalton, the Ohio Division of Natural Resources, the Ohio EPA, and EPA's Region 5 Emergency Response Section.
  • In August 2002, ATSDR submitted all individual results to property owners with an interpretation of the results.
  • In August 2002, ATSDR released the public comment version of this document.
  • In September 2002, ATSDR met with local officials to discuss the sampling results and our conclusions and recommendations regarding the results.
  • In September 2002, ATSDR held a public meeting to discuss the results of the water and air sampling.
  • In September 2002, ATSDR performed follow-up hydrogen sulfide air screening.
  • In September 2002 - January 2003, ATSDR compiled and answered all public comments, made revisions to the final version of the document based on those comments, and released the final version of the health consultation.
  • In October 2002, ATSDR requested that the health department assist two homeowners in obtaining water treatment systems for the high levels of hydrogen sulfide found in their homes.
  • In November 2002, the Cuyahoga County Board of Health counseled two homeowners on water treatment systems.

Actions Ongoing

  • ATSDR is pursuing discussion with the federal and state regulatory and enforcement agencies to implement risk management strategies to reduce the hazard.

Actions Planned

  • ATSDR will plan, develop, and implement a health education program based upon the identified needs of community members, health care professionals, and fire/law enforcement personnel.


  1. Letter from Petitioner to ATSDR. Atlanta: US Department of Health and Human Services; November 1998.

  2. Letter from Ohio Department of Natural Resources to Cady Road resident concerning the water well complaint, NW 1/4 Section 15, Royalton Township, Cuyahoga County. Columbus, OH; May 15, 1995.

  3. Janssens A and Olds JC. Scarp associated with the Middleburg fault in Hinckley Township, Medina County, Ohio. Presented at Ohio Geological Society Second Annual Technical Symposium - "Major Natural Gas Plays of the Appalachian Basin of Ohio and Surrounding Areas" Canton, OH. Oct 19, 1994.

  4. ATSDR Public Availability Session. North Royalton, OH; May 30, 2001.

  5. ATSDR Public Availability Session and interview with residents. North Royalton, OH; May 6-9, 2002.

  6. ATSDR. Cady Road Area Site file: affidavits from residents along Cady Road. Atlanta: US Department of Health and Human Services Atlanta, GA; 1998.

  7. Ohio Department of Natural Resources. Facilities Reports. 1981-1997.

  8. Letter from Ohio Department of Natural Resources to ATSDR concerning the September 2001 ATSDR health consultation on Cady Road. October 31, 2001.

  9. Ohio Department of Natural Resources. Division of Oil and Gas Complaint Forms: resident of Cady Road. #95-001. Columbus, OH; January 1995.

  10. Ohio Department of Natural Resources. 1995-1997. Division of Oil and Gas complaint logs for Cady Road. Cleveland, OH.

  11. ATSDR Official Record of Activity. Conversation between Karen Mancl of the Ohio State University Extension and Kimberly Chapman of ATSDR. Atlanta: US Department of Health and Human Services; August 31, 2001.

  12. American Analytical Laboratories, Inc. Analytical results for order # 95-01-075. Akron, OH; January 19, 1995.

  13. Ohio Department of Health. March 2, 1995. Sample Submission Report, certification number: 12345, sample number: 95800180. Columbus, OH.

  14. Ohio Environmental Protection Agency. Division of Environmental Services. November 13, 1997. Inter-office communication and laboratory sample submission and report form.

  15. Environmental Protection Agency. Region 5, Cleveland Office. Air Sampling on Cady Road. March 16, 1998.

  16. Memo from George Bollweg, USEPA Region 5 ARTS Branch, to Ross Micham, USEPA Region 5 UIC Branch. June 12, 1998.

  17. U.S. Coast Guard. Chemical Hazard Response Information System: Methane; 2001.

  18. HSDB. Accessed July 2002. Methane. Compiled by the National Library of Medicine, Department of Health and Human Services. 1988-2002.

  19. ACGIH. Documentation of the Threshold Limit Values and Biological Exposure Indices, 6th ed. Am Conference of Govt Ind Hyg, Inc, Cincinnati, OH; 1991.

  20. Ashford R. Ashford's Dictionary of Industrial Chemicals. Wavelength Publications, Ltd, London, England; 1994.

  21. Clayton GD & Clayton FE (Eds). Patty's Industrial Hygiene and Toxicology, Vol 2B, Toxicology, 4th ed. New York, NY: John Wiley & Sons; 1994.

  22. EPA. Standard Operating Safety Guides. "Atmospheric Hazard Action Guides". Office of Solid Waste and Emergency Response. Publication 9285.1-03; June 1992.

  23. HAZARDTEXT (R) - Hazard Management: Methane. 2001. Tomes CPS. Atlanta, GA.

  24. Kizer KW: Toxic inhalations. Emerg Med Clin North Am 1984; 2:649-666.

  25. CHRIS: CHRIS Hazardous Chemical Data. US Department of Transportation, US Coast Guard, Washington, DC (CD-ROM Version), Micromedex, Inc, Englewood, CO, edition expires 4/30/96.

  26. Hopkins RM & Krantz JC Jr: Anesth Analgesia 1968; 47:56-67.

  27. ATSDR. Toxicological Profile for Hydrogen Sulfide. Atlanta: US Department of Health and Human Services; 1999.

  28. Ohio State University. Hydrogen sulfide in drinking water fact sheet. AEX-319-97. Columbus, OH; 2001.

  29. Virginia Cooperative Extension. Household water quality: hydrogen sulfide in household water. Publication Number 356-488. Virginia Polytechnic Institute and State University.

  30. Jappinen P, Vilkka V, Marttila O, Haahtela T. 1990. Exposure to hydrogen sulfide and respiratory function. Br. J. Ind. Med. (47):824-828.

  31. Spolyar LW. 1951. Three men overcome by hydrogen sulfide in starch plant. Ind. Health Monthly. 11(8): 116-117.

  32. Bhambhani Y, Singh M. 1991. Physiological effects of hydrogen sulfide inhalation during exercise in healthy men. J Appl Physiol 71(5):1872-1877.

  33. Bhambhani Y, Burnham R, Snydmiller G, et al. 1994. Comparative physiological responses of exercising men and women to 5 ppm hydrogen sulfide exposure. Am Ind Hyg Assoc J 55:1030-1035.

  34. Bhambhani Y, Burnham R, Snydmiller G, et al. 1996a. Effects of 10-ppm hydrogen sulfide inhalation on pulmonary function in health men and women. J Occup Environ Med 38:1012-1017.

  35. Bhambhani Y, Burnham R, Snydmiller G, et al. 1996b. Effects of 5 ppm hydrogen sulfide inhalation on biochemical properties of skeletal muscle in exercising men and women. Am Ind Hyg Assoc J 57:464-468.

  36. Ahlborg G. 1951. Hydrogen sulfide poisoning in the shale industry. Arch. Ind. Hyg. Occup. Med. 3:247-266.

  37. D Campagna, S Kathman, R Pierson, et al. Impact of ambient hydrogen sulfide and total reduced sulfur levels on hospital visits for respiratory diseases among children and adults in Dakota City and South Sioux City, Nebraska. American Thoracic Society - ATS 2001, 97th International Conference, San Francisco, California, USA, 2001.

  38. ATSDR. Toxicological Profile for Benzene. Atlanta: US Department of Health and Human Services; 1997.

  39. U.S. Environmental Protection Agency. Spring/Summer 1998. Inside IAQ, EPA's Indoor Air Quality Research Update. A comparison of indoor and outdoor concentrations of hazardous air pollutants. EPA/600/N-98/002. Research Triangle Park, NC.

  40. American Water Works Association, Water Quality and Treatment: A Handbook of Community Water Supplies, 4th Ed. F.W. Pontius Technical Editor, McGraw-Hill Inc. 1990.


Prepared by:

LT Jennifer A. Freed, MPH
Environmental Health Scientist

Technical Assistance:

Lynn Wilder, MS, CIH
Industrial Hygienist

CDR Danielle DeVoney, PhD, PE
Senior Toxicologist, Engineer

Greg M. Zarus, MS
Atmospheric Scientist

Reviewed by:

Donald Joe, PE

John E. Abraham, PhD, MPH

Mark Johnson, PhD
Senior Representative
ATSDR/ORO/Region 5


Site Map


Sample Collection

Water sampling

Water samples were collected before any filtration or treatment systems to represent a worst-case scenario. Before sample collection, the well water was flushed (approximately 15 minutes) until relatively constant readings of temperature and conductivity were observed.

VOC, dissolved gas, and hydrogen sulfide samples were all collected in 40-ml glass containers with a PTFE-lined septum and an open top screw cap. Containers were filled in such a manner that no air bubbles were passed through the sample (i.e., very low water flow from the tap). However, bubbles were observed in the samples after the sample was collected due to off-gassing. Three glass containers were filled to reduce the odds of the development of bubbles (in the same sample number) for each sample location, but all samples developed bubbles because of the high levels of dissolved gases. Samples were placed in Ziploc™ containers and placed on ice (or kept at 4º C) until analysis and were analyzed within 10 days of collection.

Semi-VOC samples were collected in 1-liter glass amber containers, with PTFE-fitted screw caps. After filling, the jars were placed on ice (or kept at 4º C) until sample extraction. Samples were extracted within 5 days of their receipt by the laboratory and analyzed within 40 days of extraction.

Metal samples were collected in glass containers. Samples were preserved with nitric acid and placed on ice (or kept at 4º C) from the time of collection until laboratory analysis.

Sample collection, storage, and analysis description were documented on the chain-of-custody forms. The original forms were sent to the laboratory with the samples and copies of the forms were kept with ATSDR staff. A logbook recorded all comments and observations associated with sample collection.

The total number of water samples collected for this exposure investigation is displayed in the following table.

Water sample No. of Wells* Pond Duplicates Blanks Total Samples
VOCs 10 -- 1 1 12
SVOCs 10 -- 1 1 12
Metals 10 1 2 1 14
Inorganic Anions 10 1 2 1 14
Dissolved gases 10 1** 1 1 13
Hydrogen sulfide 10 -- 2 1 13
Total number of samples 60 3 9 6 78

* Includes one sample from a hand-pump well that is used only for recreational purposes. Questionnaire was not administered for this well.
** Instead of dissolved gas, total oil and grease was analyzed for the pond sample, due to a visible observation of an oily sheen.

Air Screening

Air monitors were used to screen indoors and outdoors for elevated levels of combustible gases (lower explosive limit/oxygen meter), hydrogen sulfide, methane, and volatile organics (photo-ionization detector) during water and air sampling activities. Other locations were monitored throughout the house. Monitoring locations, times, and readings were recorded on the property-specific air screening log (see Attachment A in Appendix C).

Screening results were used to determine where to collect the time-weighted average air samples. The screening results were also used to determine if airborne contaminants were from soil gas, private wells, or both. All of the homes that had basements had the highest levels of gases in the basement near the wash tub, or where the water was being flushed. Therefore we collected the eight hour samples in the basement where gases were detected.

Air Sampling

One eight-hour time-weighted-average air sample was collected in each home using SUMMA® canisters according to EPA Method TO-15.

Attempts were made to avoid sampling in areas with other known sources of VOCs (e.g., near garage where gasoline is stored and near areas where solvents or cleaning products are stored). Screening with a PID ensured that there was little contribution of these sources.

Three (total, not per home) outdoor eight-hour time-weighted average air samples were collected at three locations on the road - near the top, middle and bottom of the road.

One grab sample was taken near an uncapped wellhead because screening instruments detected explosive levels. The objective of this sample was to determine the composition of the gases that are present in the well water.

Sample collection, storage, and analysis description were documented on the chain-of-custody forms and the logbook. The original chain-of-custody forms were sent to the laboratory with the samples. Copies of the forms were made and kept by ATSDR prior to shipment.

The number of air samples collected for this exposure investigation is displayed in the following table.

Air samples Homes Well Duplicates* Blanks Total Samples
VOCs - indoor 9 1 1 1 12
VOCs - outdoor 3 -- -- -- 3
Total number of samples 12 1 1 1 15

* Actual duplicates of air cannot be collected, but two were co-located at one residence

Sample Handling and Storage

Samples were handled, stored, and shipped in accordance with applicable EPA and DOT guidelines.

Laboratory Analysis

Laboratory analysis was coordinated through an Interagency Agreement with the Division of Federal Occupational Health (FDOH), who contracted with DataChem of Salt Lake City, UT, for analysis.

Water samples were analyzed for VOCs (EPA method 8270C), SVOCs (EPA method 8260B), metals (EPA method 200.7), inorganic anions (EPA method 300.0), hydrogen sulfide (EPA method 376.1), and for the dissolved gases methane, ethane, and ethene (ATSM Method RSKSOP-175M).

Air samples were analyzed for VOCs according to EPA method T0-15. The laboratory was also instructed to analyze for methane, ethane, butane, and pentane. A late request was made for hydrogen sulfide analysis because it was detected during monitoring while in the field.

Water and air screening instruments were calibrated and provided through the Interagency Agreement with the Division of Federal Occupational Health.


One blank sample was collected for each set of water samples (VOCs, SVOCs, metals, hydrogen sulfide, gases, and inorganic anions). Distilled, deionized water was used for the blanks. These samples were prepared prior to private well sample collection and stored in the same container as other samples for the duration of the Exposure Investigation effort. Samples were not marked as blanks to avoid possible bias in laboratory reporting.

A few duplicate water samples were collected because of the off-gassing observed in the water samples. Samples were not marked as duplicates to avoid possible bias in laboratory reporting. Results of duplicate samples can be used to determine the validity of sample analysis results, as specified by the individual method (e.g., samples should be within +/- 30% of each other).

For the air samples, one SUMMA® canister remained empty to serve as the field or trip blank.

Sample collection, storage, and analysis description were documented on the chain-of-custody forms. The originals of these forms were sent to the laboratory with the samples and copies were kept by ATSDR staff. Laboratory analysis was conducted with method-specific QA/QC requirements.

Residential Interviews and Consent Forms

A questionnaire was administered to the residents of nine homes that were sampled during the exposure investigation. The questions were asked before or during the sampling event. A copy of the questionnaire can be found in Attachment B of Appendix C. Consent from the property owner was obtained prior to sampling. A copy of the consent form can be found in Attachment C of Appendix C.


Click here to view Appendix C in PDF format (PDF, 69KB)

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  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #