ALCO CONTROLS (HSI# 10099)
HAZELHURST, JEFF DAVIS COUNTY, GEORGIA
The Alco Controls facility is at 400 East First Avenue in the eastern portion of Hazlehurst, Jeff Davis County, Georgia. The facility occupies approximately 7.5 acres and is currently used to manufacture filter dryers for the refrigeration industry. The facility consists of a main manufacturing building (Building No. 2), an assembly and packing building (Building No. 1), and additional small structures used for maintenance activities. A water reservoir, used to support the facility's fire protection system, is also on site.The property is in a mixed industrial and residential area of Hazelhurst.
In August 1993, the Environmental Strategies Corporation (ESC) conducted an initial site evaluation of the facility. Over the next six years, ESC conducted several, phased investigations on soil and groundwater on and off site to determine what areas were potentially contaminated from past operations. In 1996, the Georgia Environmental Protection Division (GEPD) reclassified Alco as a Class 1 Site. Class 1 Sites have either a known human exposure, continuing releases, or are causing serious environmental harm. GEPD also formally proposed a consent order to legally bind the responsible parties to take timely actions to correct problems at the site .
Between January and March 1997, investigations focused on the former vapor degreaser pit and the residential areas north and northeast of the property. That was the fourth in a series of investigations conducted to characterize the vertical and horizontal movement of volatile organic compounds (VOCs) in groundwater. Because the extent of groundwater contamination was not fully identified during that testing, a fifth investigation was conducted between November and April 1998. Through that investigation, ESC identified the former degreaser pit as a primary source of groundwater contamination. The pit is a concrete vault constructed approximately 5 feet below ground surface (bgs). Most of the trichloroethylene (TCE) release occurred below the shallow water table on the Alco property. The distribution of TCE extends off site north to a unnamed tributary of Gully Creek, east beneath the Hazlehurst Textile property, and beyond L Street. The chemical's highest levels were detected in on-site monitoring wells east of Building No. 1 and northeast of the degreaser pit on the Gill Street right of way. TCE concentrations were 220,000 micrograms per liter (µg/L) at the building and 240,000 µ/L at the degreaser pit. A separate TCE plume was also located on the southeast portion of the Alco property. That plume extends 250 feet southeast. Cis-1,2-dichloroethylene, a TCE breakdown product, had a similar distribution in the lower sand unit groundwater. Vinyl chloride movement in the lower sand unit was not as wide spread and generally restricted to the boundaries of the Alco property.
Currently, an interim measure groundwater remediation system is operating off-site. The system is designed to control the spread of the plume and to lower the concentration of contaminants in groundwater. This pump and treat system consist of wells, water piping, and a pretreatment system. Residents are concerned about possible adverse health effects from exposure to contaminanted groundwater vapors entering their homes, about potential accidental releases from treating groundwater off-site, and past irrigation of lawn and gardens. This document reports the evaluation of public health issues that are relevant to this site. Recommendations are listed in this document that are intended to protect the health of people who live near the site.
In determining whether health effects could occur as a result of contamination from a site, first a completed exposure pathway must be identified. A completed exposure pathway means that contaminants released into the environment through the air, water, or soil have reached a point where people are coming into contact with the contaminants. Contact may occur when people drink contaminated well water, irrigate lawns and gardens with tainted water, or breathe vapors from VOCs present in water. Some questions we consider when investigating chemical exposures and their potential health effects are: (1) what is the level or concentration of the chemical that people are contacting; (2) how are people contacting the chemical (breathing, eating, drinking, or touching); and (3) is the chemical known to cause health effects at these levels from the way people are coming in contact with it?
At this site, GEPD requested that the Georgia Division of Public Health (GDPH), Health Hazards Consultation Unit, assist in determining if workers or residents living near the Alco Controls (HSI# 10099) site may have been exposed to environmental contaminants released from past, present, or future operations and if so, whether that exposure is likely to cause harm. The points of exposure were evaluated on and off site for this health consultation.
The city of Hazelhurst has two public wells that supply residents within the city limits with drinking water. The wells are drilled 860 feet and 950 feet into the Floridian aquifer . The primary water supply well is 2,300 feet northwest and up gradient of the Alco site. The city's backup well, on North Gill Street, is 1,500 feet northeast and down gradient of the site. An analysis of the backup well's raw water did not detect any VOC contamination . However, the city water department closed the backup well indefinitely as a precautionary measure. Additional groundwater samples taken at depths below the lower sand unit did not contain VOC contamination.
To determine if any groundwater was being used by the potentially affected residents, ESC conducted door-to-door well surveys in the areas north, east, and southeast of the Alco property. The well surveys were conducted in February 1997 and September 1999. ESC found a total of six, residential irrigation wells in the area. Residents used those wells primarily to irrigate lawns. The irrigation well water was drawn from the lower sand unit . Samples taken from three irrigation wells contained vinyl chloride, trichloroethylene (TCE), and a form of dichloroethylene (DCE) (Table 1). Alco Controls contacted well owners and offered to provide connection service to the public water supply. Property owners identified either connected to the municipal water supply or discontinued using their irrigation well. However, the wells have not been properly abandoned.
We do not know how long, or when, the irrigation wells became contaminated. Because the irrigation wells were primarily used for watering lawns and possibly gardens, the primary route of exposure (the way people contacted the chemicals) was through inhalation. Skin contact was also a possibility, although with the specific chemicals found, skin contact would not contribute a great deal more to the exposure unless people are using the water to fill swimming pools. If water was used to water gardens, the possiblity of the chemical building up on vegetables would be negligible. The chemicals do not accumulate in plants, and once exposed to air, they evaporate rapidly.
VOCs usually breakdown over several days or weeks if the source is eliminated, but TCE can remain in groundwater for many years. Wells #2 and #3 contain very high levels of TCE and should not be used at all, even to water lawns or gardens; however, unless people were outside and were near the water when it was running, they were not likely to inhale enough of the TCE to develop adverse health effects. If, on the other hand, people watered lawns by hand, then those people could have inhaled a substantial amount of TCE while watering. The exposure doses would have depended upon the length of time the water was running and the number of times a week that the water was used. Because we cannot reasonably estimate doses without further information on how the owners of wells #2 and #3 used the water, we are providing general health information about the VOCs of concern found in the wells (see Tables in the Appendix).
A potential exposure pathway remains for people who live over the groundwater contaminant plume. Indoor air monitoring of Building 1 on site (see the following discussion) suggests that VOCs present in the groundwater are migrating as soil gas and entering the building at low levels. People living over the plume could have contaminants entering their homes through soil gas intrusion. However, based on soil structure and the groundwater's distance below ground surface in the residential areas, the indoor air route of exposure was not identified during the risk assessment as a completed exposure pathway off site. Groundwater contamination under the residential area is said to be confined to the lower sand unit aquifer, which is 15 to 45 feet bgs. Off site, contaminanted groundwater is separated from the ground surface by the upper sandy clay unit, which is a soil formation composed of light brown to gray and fine to medium-grained sand and clay soils. Figure A is a cross section of soil units that begins on the southeastern portion of the Alco property (point A) and then moves in a north to northeasterly direction to Third Street (point A). Soil gas moves more easily through loose, sandy soil than through tight clay soil. VOCs detected in groundwater tend to decrease as they migrate off site. Groundwater VOC levels off site ranged from >1 µg/L ( 1 part per billion) to >100,000 µg/L (100,000 parts per billion). Residential areas near the facitity have the highest VOC concentrations in groundwater off site; therefore, as a precautionary measure, if homes have crawl spaces, leaving the crawl space vents open would help reduce levels that could potentially enter homes.
On December 9, 1999, indoor air monitoring was conducted at the Alco facility to estimate levels of contaminants that occupants and workers were breathing. The sampling was conducted to determine if VOCs present in shallow groundwater were migrating into the building. Air samples were collected at three locations within the offices in Building No. 1. Those offices were chosen because of their proximity to the degreaser pit, which is the main contaminant source. Samples were collected in each room at a height of 3.5 to 4 feet above the ground to estimate the breathing zone exposure for a person seated in the office.
Sample analysis showed several chemicals were present in indoor air. The chemicals were compared with ATSDR comparison values to determine if a chemical should be further evaluated for health effects. Comparison values are contaminant concentrations that are found in specific environmental media (air, soil, and drinking water) that are used to select contaminants for further health evaluation (see Appendix D). Exposures below these levels are considered safe. Table 2 lists the contaminants of concern in Building No. 1 that were selected for further review .
All chemicals in indoor air were below the Agency for Toxic Substances and Disease Registry's (ATSDR) minimal risk levels (MRL). The MRL is a dose below which noncancerous health effects are not likely to develop in people exposed to that chemical over a specified period of time. Additionally, we reviewed the toxicological profile of each known or probable human carcinogen present in Building No. 1 to provide any data relevant to understanding current exposure. The following discussion provides information about inhalation of the chemicals of concern on and off site. Additional facts are in Appendix B.
- The International Agency for Research on Cancer (IARC) has classified vinyl chloride as a human carcinogen. The United States Environmental Protection Agency (EPA) has also determined that vinyl chloride is a known human carcinogen.
- The highest concentration in an irrigation well was estimated at 91 µg/L, which is 0.091 ppm.
- One part per million is the maximum average amount of vinyl chloride allowable in workplace air during an 8-hour work day in a 40-hour week.
- The concentration measured in indoor air in Building No. 1 was 1.2 µg/m3, which is 0.00046 ppm.
- ATSDR's intermediate inhalation MRL for noncancerous health effects is 0.03 ppm.
If you breathe high levels (8,000 ppm) of vinyl chloride for a short time, you will probably feel dizzy or sleepy and may pass out. These effects occur within five minutes. Recovery is expected to be rapid if exposure is stopped and fresh air is breathed. Some people who breathed vinyl chloride over several years had damaged livers. The damage was more likely to develop from exposure to high levels of vinyl chloride. Some people who worked with vinyl chloride developed nerve damage, and others developed an immune reaction. The lowest levels of vinyl chloride that cause liver changes, nerve damage, and the immune reaction in humans are not known. In studies, increased incidence and severity of elevated blood pressure and endema during pregancy were found in female workers exposed to vinyl chloride when compared to unexposed workers. Exposures ranged from 0.2 ppm to 130.7 ppm. No other information was given about those exposures. Those exposures are much greater than the levels found in indoor air in Building 1.
Vinyl chloride is known to cause cancer in humans. A large number of studies have reported a greater than expected incidence of a rare type of cancer, angiosarcoma of the liver, among occupationally exposed workers. Other forms of cancer have also been linked to vinyl chloride inhalation. These results are based on studies of workers who breathed high levels of vinyl chloride for many years before occupational standards were made more rigorous. Animal studies also support those findings. In one study, rats exposed to as low as 5 ppm vinyl chloride for 52 weeks showed an increase in the incidence of mammary gland carcinomas .
- IARC has classified benzene as a human carcinogenand EPA has determined that it is a known human carcinogen.
- The concentration measured in indoor air in building one was 3.06 µg/m3, which is 0.00095 ppm.
- One part per million is the maximum allowable average amount in workplace air during an 8-hour work day in a 40-hour week.
- Levels in the range of 700-3,000 ppm during short term exposures can cause drowsiness, dizziness, rapid heart rate, headaches and unconsciousness. In most cases, symptoms disappear when exposure stops, and the person begins to breathe fresh air.
- ATSDR's intermediate inhalation MRL for noncancerous health effects is 0.004 ppm.
Long-term exposure to relatively high levels of benzene in air can cause cancer of the blood forming organs, a condition called leukemia. Exposure to benzene has been asssociated with development of a particular type of leukemia called acute myeloid leukemia. At least one study revealed that very low levels of benzene exposure produce no adverse effects on the bodies ability to produce blood. Workers in a Texas refinery showed no changes in blood cells in people exposed at 0.53 ppm for 1-21 years. A cancer effect level of 2 ppm was associated with the developement of acute erthyroid luekemia, another form of the disease.
- IARC has not classified TCE as a human carcinogen
- The highest concentration reported in an irrigation well was 21 ppm.
- Animals with a chronic inhalation exposure of <100 ppm showed no adverse, noncancerous health effects.
- The concentration measured in indoor air in building one was 17.47µg/m3, which is 0.0035 ppm
- One hundred parts per million is maximum allowable average amount in workplace air during an 8-hour work day in a 40-hour week.
- ATSDR's chronic inhalation MRL for noncancerous health effects is 1 ppm.
TCE mostly affects the nervous system. People who breathe moderate levels (200 ppm) of TCE for short time periods may have headaches, dizziness, or impaired ability to perform. Skin contact with high levels may cause rashes. Liver effects have been reported in occupationally exposed workers. Exposure concentrations in those studies were not reported. Health effects for long-term exposures have mostly been studied in animals. Animals exposed to moderate levels of TCE had enlarged livers. Higher exposures caused liver and kidney damage. We do not know if TCE causes birth defects or affects our ability to reproduce; studies have had varied results. More research is needed to make a clear determination on whether TCE causes cancer. 
- EPA has determined cis 1,2 DCE is not classifiblable as a carcinogen.
- The highest concentration reported in an irrigation well was 0.76 ppm.
- Intermediate (exposure longer than two weeks but less than one year) inhalation exposure of 200 ppm showed subtle, noncancerous adverse health effects in animals.
- The concentration measured in indoor air in Building No. 1 was 32.64 µg/m3, which is 0.0082 ppm.
- Two hundred parts per million is the maximum allowable average amount in workplace air during an 8-hour work day in a 40-hour week.
- ATSDR's chronic inhalation MRL for noncancerous health effects is 0.2 ppm.
Breathing high levels of cis-1,2 DCE (1,200 to 2,200 ppm) can make you feel nauseous, drowsy, and tired. You can smell DCE at about 17 ppm in air. The long-term (365 days or longer) human health effects after exposure to low concentrations are not known. One animal study suggested that an exposed fetus may not grow as quickly as one that has not been exposed. However, exposure has not been shown to affect fertility in people or animals. When animals breathed high levels of trans-1,2-DCE, another form of DCE, for a short or long period of time, their livers and lungs were damaged, and the effects were more severe with longer exposure times .
Community concerns are as follows.
Concern: Will the interim control measure leak and contaminate the area?
Response: The contractor and facility have taken serveral measures to ensure the environment and people are not impacted by the pretreatment facility operations. Currently, groundwater is pumped through underground piping to a pretreatment facility constructed on a leased parcelof land owned by the city of Hazelhurst. Piping located in areas without detectable VOCs in the groundwater consist of double containment piping to prevent releases of untreated groundwater into unimpacted groundwater. The entire system will automatically shutdown under specific conditions and alert the Alco facility .
Concern: Communitymembers are concerned about the possible links to cancer from coming in contact with the chemicals migrating off site.
Response: Generally, one in four people develop some kind of cancer during their lifetime, and we do not know what causes most cancers. Age, diet, gender, and race are also risk factors to consider with certain forms of cancer. People may have likely been exposed to contaminants in the past from using private irrigation wells. Because the water was not being used for any household or domestic purposes, exposure likely would have been short in duration. Samples taken from three irrigation wells contain contaminants above federal drinking water standards. The route of exposure of most concern at this site is inhalation of the VOCs as they evaporate from the water. If people are watering their lawns by hand, their exposure to the VOCs could be enough to increase their risk of developing cancer. For that reason, wells #2 and #3 should not be used at all. Low levels of contaminants were present in indoor air at Building No. 1. Occupants are currently exposed to levels of contaminants that are not likely to increase their risk of developing cancer over a long period of time.
Concern: Are contaminants from the groundwater plume migrating into indoor air in homes?
No data are available from nearby homes that are over the groundwater plume to determine if VOCs are entering indoor air from soil gas. VOCs were not sampled for in indoor air or in soil gas. VOCs detected in groundwater tend to decrease as they migrate off site. Groundwater VOCs concentration off site ranged from >1 µg/L to >100,000 µg/L. Residential areas near the facility have the highest VOC concentrations in groundwater off site; therefore, as a precautionary measure, if homes have crawl spaces, leaving the crawl space vents open would help reduce levels that could potentially enter homes.
The levels of contaminants in wells #2 and #3 posed a public health hazard for people who hand watered lawns. The wells are no longer used for irrigation, but the wells have not yet been properly abandoned. Soil gas intrusion into homes has not been investigated. Indoor air currently poses an indeterminate public health hazard for nearby residents. Good ventilation can reduce the levels (if any) of contaminants entering homes through soil.
Although current indoor air levels of contaminants in Building No. 1 pose no apparent public health hazard, two of the contaminants found in air inside the building are known human carcinogens. Although the levels found in the air are below levels known to cause cancer, prudent public health practice is to reduce exposure to known carcinogens as much as possible.
Local officials should ensure irrigation wells remain unused and are properly abandoned. Well drilling should not be permitted in the contaminated area.
Conduct soil gas sampling in selected areas off site to determine if vapors are migrating through the soil.
The facility owner should provide monitoring well and pretreatment system operational data to GEPD to ensure groundwater remediation is effectively working and that no one is exposed to contaminants as a result of faulty operations.
GDPH will conduct community educationfor residents in the affected area.
1. ALCO Controls Division Facility, Hazelhurst, Georgia, Revised Compliance Status Report, Environmental Strategies Corporation, December 28, 1999
2. Letter to Mr. William Parnell, RE: Public Comments Corrective Action Plan Alco Controls Site, Hazelhurst, Jeff Davis County HSI# 10099
3. Alco Controls Division Facility, Hazelhurst, Georgia, Proposed Corrective Action Plan, Environmental Strategies Corporation, December 28, 1999
4. Groundwater Sampling Result-Lower Sand Unit, Alco Controls Facility, Hazelhurst, GA. Environmental Strategies Corporation, February 1999
5. Agency for Toxic Substances and Disease Registry, U.S. Public Service: Toxicological Profiles on September 1997
6. Reveiw of the Revised Compliance Status Report (CSR) for the Alco Controls Division Facility, Hazelhurst, HSI # 10099, Georgia Environmental Protection Division, Risk Assessment Unit, June 29, 2000.
7. Interim Measures Work Plan Off Property Hydraulic Containment System (Draft), Environmental Strategies Corporation, December 22, 1999
8. Agency for Toxic Substances and Disease Registry, ToxFAQs, Vinyl Chloride, September 1997
9. Agency for Toxic Substances and Disease Registry, ToxFAQs, Trichlorethylene, September 1997
10. Agency for Toxic Substances and Disease Registry, ToxFAQs, 1,2-Dichloroethene, September 1997
Maurice Redmond, Consultant
Health Hazards Consultation Section
Georgia Division of Public Health
Bill Williams, Environmental Engineer
Hazadous Sites Response Program
Georgia Environmental Protection Division
ATSDR Technical Project Officer
Gail Godfrey, Environmental Health Scientist
Division of Health Assessment and Consultation
ATSDR Regional Representative
Robert Safay, Senior Representative
The Georgia Department of Human Resources, Division of Public Health prepared Alco Controls Health Consultation under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.
Gail D. Godfrey
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this health consultation and concurs with the findings.
Lisa C. Hayes
for Chief, SPS, SSAB, DHAC, ATSDR
Concentration reported in well
Concentration reported in well
Concentration reported in well #3
Comparison Value (air*)
Comparison Value (drinking water)
|TCE||4.4||1,500||21,000||100 EMEG||5 MCL|
|1,1 DCE||5.1||ND||5.1||0.005 CREG||0.06 CREG|
|Trans -1,2 DCE||ND||2.6||6||200 EMEG||100 MCL|
|Vinyl Chloride||ND||ND||91J||0.08 CREG||0.02 CREG|
1 Analytical results of water samples from 3 residential irrigation
2 ppb = parts per billion
CREG = Cancer Risk Evaluation Guide
MCL: Maximum Contaminant Level
EMEG: Environmental Media Evaluation Guide
ND = Not detected
NA = Not available
* Air comparison values are provided because inhalation is the route of exposure of concern. If 100% of the level of contaminant volatilized at one time, levels of contaminants in air at the point emitted from the well water would exceed comparison values.
Maximum Concentration Detected
ATSDR Comparison Value
Georgia Threshold for Continuous Exposure
|Trichlroethene||17.47||537.4 (intermediate EMEG4)||537,423||640|
|Vinyl chloride||1.2||0.1 (CREG)||2,567||31|
1 µg/m3 = micrograms per cubic meter
2 CREG = Cancer Risk Evaluation Guide
3 PEL = Permissible Exposure Level
4 INTER. EMEG= Intermediate Environmental Evaluation Guide
|Pathway Name||Source||Medium||Exposure Point||Exposure Route||Receptor Population||Time of Exposure|
|Inhalation of VOCs from irrigation well water||well water||air||air immediately around sprinklers and spigots used for irrigation||inhalation,
|On-site soil gas intrusion of VOCs released from groundwater||soil gas/ groundwater||air||Building 1||inhalation||Employees
* The approximate number of exposed individuals is the estimate of persons who were employed at the facility during the duration of suspected contamination.
|Pathway Name||Source||Medium||Exposure Point||Exposure Route||Receptor Population||Time of Exposure|
|Soil gas intrusion of VOCs released from groundwater||soil gas/ groundwater||air||inside homes||inhalation||<15||Past
- Exposure to vinyl chloride happens mostly from breathing contaminated air in the workplace or near plastics industries, hazardous waste sites, and landfills.
- Vinyl chloride is a colorless vapor with a mild, sweet odor. It is in liquid form if kept under high pressure. Most of the vinyl chloride produced in the U.S. is used to make polyvinyl chloride (PVC).
- It evaporates rapidly from surface water or soil and it breaks down in air in a few days. Little dissolves in water and it doesn't form other harmful chemicals.
- The EPA requires levels of vinyl chloride in drinking water to not exceed 2 parts of vinyl chloride to one billion parts of water (2 ppb).
- Occupational Safety and Health Admistration regulates the level of vinyl chloride in the workplace. One ppm is the average amount of vinyl chloride allowed in workplace air during an 8-hour work day in a 40-hour week.
- ATSDR's Toxicological Profile showed a no observable adverse non cancerous effect level in animals with a chronic inhalation exposure of 10 ppm and a chronic oral exposure dose of 1.7 mg/kg/day.
- Benzene is a colorless liquid with a sweet odor. It evaporates into air very quickly and dissolves slighty in water. Most people can smell benzene in air at 1.5-4.7 part per million and in water at 2 ppm.
- Benzene was first discovered and isolated from coal tar in the 1800's. Today benzene is made mostly from petroleum sources.
- The major source of benzene exposure are tobacco smoke, automobile service stations, exhaust from motor vehicles and industrial emissions. Vapors from products that contain benzene, such as glues, paints and funiture wax can also be sources.
- The EPA requires levels of benzene in drinking water to not exceed 5 parts of benzene to one billion parts of water (5 ppb).
- Trichloroethylene is a nonflammable, colorless liquid at room temperature with a somewhat sweet odor and a sweet, buring taste. Most people can smell it in the air at low levels.
- TCE was once used as an anesthetic for surgery, but it is now used mainly as a solvent to remove grease from metal parts. It is also found in some household products like typewriter correction fluid, paint removers, adhesives, and spot removers.
- It evaporates into the air during grease removal operations and from soil and surface water.
- It breaks down in air in a few weeks, in surface water in days to weeks and more slowly in deep soil.
- The EPA requires levels of TCE in drinking water to not exceed 5 parts of TCE to one billion parts of water (5 ppb).
- Occupational Safety and Health Admistration regulates the level of TCE in the workplace. 100 ppm or 100,000 ppb is the average amount of TCE allowed in workplace air during an 8 hour work day in a 40 hour week.
- ATSDR's Toxicological Profile showed a no observable adverse effect level in animals with a chronic inhalation exposure of 100 ppm and a chronic oral exposure dose of 50 mg/kg/day.
- cis-1,2-Dichloroethene is a highly flammable, colorless liquid with a sharp, harsh odor and evaporates rapidly into air. You can smell 1,2-DCE in air at about 17ppm.
- It can travel through soil or dissolve in water in the soil. In groundwater, it takes about 13-48 weeks to to break down. There is a slight chance that 1,2 dichlorethene will break down into vinyl chloride.
- The EPA requires levels of cic-1,2-DCE in drinking water to not exceed 70 part of 1,2-DCE to one billion parts of water (70 ppb).
- Occupational Safety and Health Admistration regulates the level of cis-1,2-DCE in the workplace. The maximum amount of cis-1,2-DCE allowed in workplace air during an 8 hour work day in a 40 hour week is 200 ppm.
Comparison Values are contaminant concentrations that are found in specific environmental media (air, soil, and drinking water) that are used to select contaminants for further evaluation if people are exposed to the contamination. Comparison values used in this document are defined in the following paragraphs.
Cancer Risk Evaluation Guide (CREG) is the estimated contaminant concentration that would be expected to cause no more than one excess cancer in one million (1 x 10-6) persons exposed over a lifetime (70 years). CREGs are calculated using the U.S. Environmental Protection Agency's cancer slope factors.
Environmental Media Evaluation Guide (EMEG) is based on minimal risk levels (MRLs). Contaminants present in environmental media below the EMEG are safe levels.
Reference Dose Media Evaluation Guide (RMEG) is based on the Environmental Protection Agency's (EPA) Reference Dose. Like the EMEG, contaminants present in environmental media below the RMEG are safe levels.
Maximum Contaminant Levels (MCLs) are the maximum permissible levels of contaminants allowed in public water supplies. The U.S. Environmental Protection Agency (EPA) deems exposure over a lifetime (70 years) to the MCL protective of public health at an exposure rate of drinking 2 liters of water per day for an adult and 1 liter of water per day for a child. In establishing MCLs, EPA is required to consider factors, such as whether the technology is available to achieve the level, in addition to public health factors.
A Minimal Risk Level (MRL) is an estimate of daily human exposure to a chemical (in milligrams/kilogram/day) that is likely to be without an appreciable risk of harmful effects (noncarcinogenic) over a specified duration of exposure. MRLs are based on human and animal studies of noncancer effects and are reported for acute (14 days), intermediate (15-364 days), and chronic (365 days) exposures. Where sufficient toxicological information is available, the Agency for Toxic Substances and Disease Registry (ATSDR) has derived MRLs for inhalation and oral routes of exposure at each duration of exposure (acute, intermediate, and chronic). MRLs are published in ATSDR's Toxicological Profiles for specific chemicals.
Exposure Doses are derived by calculating the amount of a contaminant that is taken into the body of an exposed person over a period of time. The following equation is used to estimate the exposure doses resulting from ingestion of contaminated groundwater:
|IDw =||exposure dose water|
|C =||contaminant concentration (highest level found in a specific medium)|
|IR =||intake rate of contaminated medium (based on average ingestion rates of 2 liter/day for adults; 1 liter/day for children)|
|BW =||body weight (based on average weights for adults: 70 kg ; children: 10 kg)|
The inhalation dose is equal to the concentration of the contaminant in air; therefore, no calculation is needed to determine the inhalation dose.