PUBLIC HEALTH ASSESSMENT
FAIRCHILD AIR FORCE BASE
SPOKANE, SPOKANE COUNTY, WASHINGTON
PATHWAYS ANALYSIS/PUBLIC HEALTH IMPLICATIONS (continued)
C. Potential Exposure Pathways
Potential exposure pathways are discussed below. A summary, background, health assessment,
conclusions, and recommendations are provided for each pathway. No specific health effects
are discussed because there is currently no exposure occurring. The pathways are discussed in
terms of contaminants of concern that are present and the potential for an exposure to occur
should the pathway become complete in the future.
| Pathway 1: Future Off-Base Development --> Groundwater --> Off-Base Residents |
Off-base areas adjacent to the Craig Road Landfill (SW-8), wastewater lagoons (WW-1) and the former fire training area (FT-1) are currently not suitable for domestic use of groundwater. TCE detected in off-base monitoring wells north and east of the Craig Road Landfill and east/southeast of the wastewater lagoons are above a level of concern. Perimeter wells at the eastern border of the FT-1 site suggest that VOCs may be present in groundwater directly east of this site. Past detections of elevated inorganic substances (metals) at the WW-1 and FT-1 sites are difficult to interpret. Elevated metals may be present in off-base groundwater east of the WW-1 and FT-1 sites.
The Craig Road Landfill (SW-8) has contaminated a large area of groundwater to the east/northeast with TCE. Groundwater contamination originating from the Craig Road Landfill is discussed extensively under completed exposure pathway 1a (page 16). The maximum off-base level of TCE ever detected in the vicinity of the landfill is 2,800 ppb found in April 1991 at MW-85 located on the northeast border of the landfill. The most recent sampling of off-base monitoring wells in this area detected a maximum of 480 ppb TCE in June 1997 at MW-118 located approximately 2,000 feet east of the landfill.
A second plume originating in the vicinity of the wastewater lagoons (WW-1) also contains TCE and has contaminated residential drinking water wells in the West Thorpe Road area. This plume is discussed more extensively under completed exposure pathway 2 (page 30). The maximum level of TCE ever detected off-base in the WW-1 vicinity is 69 ppb found at MW-120 in December 1995. The most recent sampling of monitoring wells at the WW-1 site in June 1997 site detected an off-base maximum of 45 ppb TCE also at MW-120. MW-120 is an shallow well located approximately 800 feet east of the WW-1 site that has shown increasing levels of TCE since initial sampling detected 18 ppb in April/May, 1991. MW-122 is a bedrock (Basalt A) well adjacent to MW-120 that has shown only minimal TCE contamination suggesting that the plume remains in the shallow aquifer at this point (see Figure 5).
Other VOC contaminants of concern detected off-base near the WW-1 site include vinyl chloride and cis-1,2-dichloroethylene (cis-1,2-DCE) which are both degradation products of TCE. The most recent sampling of off -base wells near the WW-1 site in June 1997 detected vinyl chloride and cis-1,2-DCE at maximum levels of 2.2 and 34 ppb, respectively. The maximum levels of these contaminants ever found on-base at the WW-1 site are vinyl chloride at 96 ppb and cis-1,2-DCE at 160 ppb.
A third plume containing primarily benzene migrating from the former fire training (FT-1) area has reached base perimeter monitoring wells but has not impacted off-base wells 800 feet east of FT-1. The FT-1 site is located on the east perimeter of the base just south of the wastewater lagoons. It is a 250-foot diameter area of gravel and sand used for fire training purposes from the early 1970s until 1990. Prior to 1970, a nearby area of open ground was apparently used for this purpose. Mock fires were staged 2-3 times per month by igniting about 300 gallons of clean or water contaminated JP-4 fuel applied from a nearby 5,000 gallon underground storage tank to aircraft and building mock-ups located in the gravel area. Approximately 125 gallons of aqueous film-forming foam (AFFF) was used to put out each fire. The aircraft mock-up was reportedly surrounded by a sand and gravel berm. Excess fuel, water, and AFFF were collected in a catch basin that flowed to an oil/water separator. The separator apparently discharged to surrounding soil. At the time of the IRP Phase I inspection in 1984, this separator did not appear to be operating properly. Soil stained areas were noted in the vicinity. Fire training operations moved to the FT-2 site area in 1990. A bioventing and air sparging system designed to remediate both soil and groundwater contamination at the FT-1 site have been operating since June 1997.
Groundwater contaminants of concern at the FT-1 site include benzene and vinyl chloride. TCE has been detected at low levels at the FT-1 site but was not detected in any 1996 sampling rounds. The presence of vinyl chloride in the FT-1 area is likely due to the degradation of TCE. The maximum level of vinyl chloride ever detected at the FT-1 site is 92 ppb found in on-base monitoring well MW-152 during March 1996 sampling. Benzene was found in MW-152 at 290 ppb during December 1996 sampling. Benzene and vinyl chloride have not been detected in off-base monitoring wells MW-124 and MW-125 located approximately 800 feet east of site FT-1. However, analysis of perimeter well samples at the FT-1 site detected 50 ppb benzene at perimeter well MW-226 in June 1996. Vinyl chloride was also detected in perimeter well MW-226 at 14 ppb in September 1996. The most recent sampling of perimeter wells at the FT-1 site in June 1997 detected benzene at a maximum of 91 ppb in MW-247 and vinyl chloride at a maximum of 9.1 ppb in MW-226. VOCs detected in wells at the FT-1 site are primarily in the shallow aquifer with only trace levels detected in Basalt A bedrock groundwater.
It should also be noted that high levels of metals have been detected in WW-1 and FT-1 area groundwater during analysis between 1986 and 1991. The maximum levels of metals detected in on-base monitoring wells are given in Appendix C Table 7. These values are from unfiltered samples of shallow monitoring wells and are suspect for sediment contamination. Filtered samples from shallow wells and unfiltered samples from bedrock wells show much lower levels. Filtered samples indicate a measure of dissolved metals but could exclude metals bound to suspended solids that can travel to drinking water wells. Unfiltered bedrock samples should be an accurate measure of metals that could reach residential wells since no fraction is excluded and sediment contamination is minimal.
Analysis of the most recent unfiltered samples taken in 1991 showed much lower levels of metals. This result could indicate a reduced amount of sediment contamination and/or reduced levels of metals in groundwater. On-base well samples were not analyzed for metals after 1991. Arsenic was detected at an off-base maximum of 66 ppb in a filtered sample from bedrock well MW-152. No other metals have been detected at levels of concern in off-base wells.
The plumes discussed above are either present in off-base groundwater or contain contaminants at levels of concern in perimeter wells and, therefore, pose a threat to off-base groundwater. Levels of TCE that have recently been detected in off-base wells east and northeast of the Craig Road Landfill and east/southeast of site WW-1 are above EPA's MCL. Perimeter wells sampled recently near WW-1 also indicate the presence of cis-1,2-DCE, trans-1,2-DCE, and vinyl chloride above MCLs. Installation and domestic use of groundwater wells in these areas could result in exposure to VOCs in drinking water via ingestion and inhalation.
The FT-1 plume may already be present in off-base groundwater but has not yet reached monitoring wells on the adjacent property 800 feet to the east. Groundwater at this property could contain vinyl chloride and benzene above levels of concern. Installation and domestic use of groundwater wells in these areas could result in exposure to VOCs in drinking water via ingestion and inhalation.
The available data for metals in groundwater at the WW-1 and FT-1 sites are difficult to interpret. Although high levels detected in the past are apparently due to sediment contamination, the WW-1 and FT-1 areas could be a source for metals in groundwater. It is possible, therefore, that groundwater east of the WW-1 and FT-1 sites is contaminated with elevated levels of metals. Installation and domestic use of groundwater wells in these areas may result in exposure to metals in drinking water via ingestion.
Groundwater in areas immediately east and north of the Craig Road Landfill (SW-8) and east of the wastewater lagoons (WW-1) and fire training area (FT-1) may not be suitable for domestic use. Elevated levels of VOCs associated with these sites have been detected in nearby off-base monitoring wells or perimeter wells. Any new drinking water wells installed in these adjacent off-base areas could result in future exposure to VOCs via ingestion and inhalation.
Data generated from past sampling of monitoring wells for inorganic substances (metals) at WW-1 and FT-1 are inconclusive. Elevated levels of metals may be migrating in groundwater from the FT-1 and WW-1 sites.
Any new groundwater wells installed on properties adjacent to the north and east boundary of the Craig Road Landfill should be restricted to non-domestic uses until remedial efforts in these areas are complete. These areas have been shown to be well within the TCE plume originating from the Craig Road landfill as demonstrated from the analysis of residential and monitoring wells. Properties located in the contaminated groundwater zone include the Vietzke Village trailer park, Whitman College property, and the Scafco Corporation property.
Any new groundwater wells installed on properties adjacent to the east boundary of the wastewater lagoons (WW-1) and fire training area (FT-1) should be restricted to non-domestic uses until remedial efforts are complete. Shallow groundwater directly east of the WW-1 site has shown increasing levels of TCE. Off-base monitoring wells east of the FT-1 site have not yet been impacted by a benzene and vinyl chloride plume extending from the FT-1 site to the perimeter of the base. This area is, however, at risk for contamination from this plume and the plume originating from the WW-1 area.
Unfiltered, low-flow samples should be taken from shallow monitoring wells (on and off-base) in
the WW-1 and FT-1 area and analyzed for metals to determine whether metals in these source areas are a threat to off-base groundwater.
| Pathway 2: Future Base Development -->Soil/Groundwater --> Future Residents |
Fairchild has identified thirty-nine contaminated sites on base. Current exposure of base personnel was evaluated above as completed exposure pathway 5. However, the potential exists for land use, in areas currently posing no apparent public health hazard, to change in the future. Future installation of water supply wells for domestic use could result in exposure to contaminants above a level of concern. Soil contamination that poses no apparent public health hazard to on-base workers could be a hazard under a residential exposure scenario. The risk posed to future residents would depend on many factors including location, date of development, and ongoing cleanup efforts. Development of base property is currently subject to review on various levels that should prevent the location of any new residential developments in areas of concern. Should the base, or any portion of the base, close in the future, any transfer of property is subject to the requirements of the USAF Base Realignment and Closure program that includes comprehensive environmental review.
On-base contamination of groundwater has been identified at various sites around the base. Six of these sites are part of a Long Term Monitoring plan (LTM) because of elevated levels of TPH, benzene and TCE in soil and groundwater. Contamination exists in both the shallow (alluvial) aquifer and upper bedrock (Basalt A) aquifer. In addition to those sites included in the LTM, groundwater contamination has been found to a lesser degree at several other sites. In general, groundwater contamination at these sites is the result of jet fuel spills/leaks, landfills, and maintenance shop waste discharge.
Groundwater on-base moves through both the shallow and bedrock aquifers in an easterly direction. Of the many groundwater contamination sites located on-base, only those sites on the eastern border of the base pose any threat to off-site wells. Those sites include the Craig Road Landfill (SW-8), wastewater lagoons (WW-1) and fire training area (FT-1) area and are discussed in completed exposure pathways 1 and 2 and potential exposure pathway , respectively. The widespread contamination from the many interior sites does, however, pose a threat to any future use of groundwater that might occur through redevelopment of the base. The contaminants of concern for on-base groundwater along with their base-wide maximum values are given in Appendix C, Table 7.
On-base contamination of soil is discussed for Fairchild personnel under completed exposure pathway 5. The same contaminants of concern identified under this pathway exist for other exposure scenarios should the base be redeveloped in the future. Since future development of the base is not predictable, a worst-case residential exposure scenario will be evaluated for exposure to contaminants of concern in groundwater and soil.
On-base areas with groundwater contamination at levels of concern include sites WW-1, FT-1, SW-1, IS-1, PS-1, PS-2, PS-8, PS-10, and the Craig Road Landfill. Development of groundwater for domestic purposes at these sites could result in exposure to VOCs and metals at levels of concern. The widespread contamination of groundwater along the flight line with TCE, TCE degradation products, benzene and TPH render this area and areas downgradient currently unsuitable for groundwater development.
Some areas on-base may also represent unacceptable health risks through contact with soil
depending on future land use. Table 4 below lists the sites that would currently be of concern for
soil exposure if redeveloped for residential use.
| Table 5. Potential Areas of Concern for Future On-Base Residential Soil Exposure Fairchild Air Force Base, Washington | |||
| Site | Description | Contaminants | Comments |
| FT-2 | Former Fire Training Area | Lead | |
| WW-1 | Wastewater Lagoons | Lead, cadmium, arsenic | Sediment samples. |
|
SW-11 |
Former Aircraft Reclamation Site | Lead, cadmium | Sub-surface cadmium and lead. |
|
SD-37 |
Underground Storage Tank | VOCs | Area of tank removal near Building 2447 |
|
SD-38 |
Wastewater Drainage Ditch | Arsenic | Drainage ditches near flight line. |
It is important to note that this assessment is based on current data. Some of these sites are undergoing remediation designed to reduce groundwater and soil contamination to below a level of concern. Conversely, some of the areas not considered to be a groundwater hazard do not have monitoring wells in the area to confirm the absence of contamination. Also, the potential hazard of VOC-contaminated groundwater is not restricted to use as a water supply. Depending on various factors, including the amount and depth of contamination, VOCs in groundwater can be a hazard through vapor infiltration directly into indoor air of homes located above a contaminated shallow aquifer. Future residential development in and around these areas should be preceded by evidence showing that contaminants in soil and groundwater are below levels of concern.
Many areas on base may not be suitable for future residential development because of groundwater and soil contamination. The base has no plans for locating future residential developments in any of these areas. In addition, any new developments on base must undergo a review process in which the base Installation Restoration Program is a part. Any transfer of property following closure of the base is subject to a comprehensive environmental review by the USAF Base Realignment and Closure program.
No recommendations are necessary relative to the potential for on-base residential development.
Fairchild and the USAF have the necessary protocols in place to prevent such development without prior environmental review.
| Pathway 3: On-Base Supply Well #2 --> Groundwater --> Base Personnel |
On-base supply well #2 is located at the southeast corner of the base. It supplies approximately one-fifth of base water needs during peak usage which occurs in the summer. Regular monitoring of this well has shown no detections of VOCs that might be related to hazardous waste releases. The potential exists, however, for VOCs to migrate from the nearby explosive ordnance (EOD) range.
The base is supplied with water from the Fort Wright well field located approximately 12 miles east of the base and on-base supply well #2 located at the southern end of the base. Both sources contribute to the base water supply with a maximum of 4,100 gal/min coming from the Fort Wright well field while on-base supply well #2 contributes varying amounts with a peak output in the summer of 1,000 gal/min 11. On a regular basis, both systems are monitored as a public water supply for VOC, SVOC, and inorganic substances.
To date, on-base supply well #2 has not been impacted by any contaminants associated with hazardous waste releases. The potential exists, however, that contaminants from the EOD range (SW-13) could migrate in groundwater and impact this well. The EOD range was used to burn and detonate explosives for an undetermined period of time. The site is located approximately 2,500 feet southeast of on-base supply well #2 and consists of a burial trench, personnel bunker, and 500-gallon fuel storage tank. Burning and detonation of explosives apparently took place within a bermed area of the site. The site is currently used only to burn materials too unstable to be transported off-site.
Soil sampling in the SW-13 area indicates moderately increased levels of lead at a maximum of 262.3 ppm. No nitroaromatic compounds were detected in soil. No groundwater sampling data are available for the SW-13 area. Although soil sampling indicates that metals and nitroaromatics are not present at high enough levels to threaten groundwater, VOC (e.g., BTEX) contaminants in the fuel used to ignite the explosives could possibly have migrated to groundwater as is the case with the FT-1 site.
Since no BTEX compounds have been detected in on-base supply well #2, it is unlikely that past burning activity will impact this well in the future. If a plume does exist in the SW-13 area, increased pumping of on-base supply well #2 could draw existing groundwater contamination into the well. No actions need to be taken with respect to water quality in on-base supply well #2. Water extracted from this well is currently tested on a quarterly basis for VOCs. If burning of explosive ordnance does continue at the EOD range, it should be done no closer to this supply well than in the past.
On-base supply well #2 has not been impacted by contaminants related to any on-base hazardous waste sites. The potential exists, however, for VOC contaminants from fuel used in the burning of ordnance at the EOD range to migrate toward this well.
No recommendations are necessary regarding the potential for contamination of on-base supply well #2. The base currently monitors on-base supply well #2 as required for a public water supply.
Trichloroethylene (TCE)
Trichloroethylene (also know as trichloroethene) or TCE is a man-made chemical that exists as a clear liquid at room temperature with a sweet odor at very high concentrations in air. TCE is used primarily as an organic solvent for cleaning grease from metal parts. It is also used as a solvent in adhesives, paint removers and some household cleaning products. TCE was formerly used as an anaesthetic and for the decaffeination of coffee. Although TCE is not a naturally occurring chemical, its widespread use has resulted in detectable levels in air and water all over the world. These levels are generally higher near urban/industrial areas. An average concentration of TCE in the air of rural/remote areas has been estimated at 0.03 ppb.15 Levels in groundwater should be below detection unless a nearby source is present.
Most of the health effects determined to result from TCE exposure have come from the study of animals. These studies have shown that rats and mice can suffer liver and kidney damage when exposed to high doses of TCE. TCE has been shown to cause liver and lung cancer in mice and kidney cancer in rats. Exposure of the developing fetus (i.e., in utero) has been shown to cause adverse developmental effects in animals. Adverse effects on the nervous system along with changes in behavior were found in rats exposed to high doses of TCE in utero. 15 Dawson et al. found fetal heart defects in rats exposed in utero at relatively low doses compared with those used in other studies. 39 A lowest observed adverse effect level (LOAEL) of 0.18 mg/kg-day was calculated from this study. This LOAEL was used to compare doses estimated from the exposure of pregnant women drinking TCE-contaminated water during pregnancy. Various other animal studies examining the non-cancer effects of long term TCE exposure in animals showed effects only at much higher doses. 15
Data on the non-cancer effects of TCE in humans are limited. At very high levels in air, TCE can cause dizziness and drowsiness. Limited evidence of liver damage in workers exposed to TCE via inhalation supports this same finding in rats and mice. Limited evidence in humans also exists to support the finding of developmental heart defects in animals. A study in Tucson, AZ, found a small increase in heart defects of children exposed in the womb to TCE when their mothers drank contaminated water. Approximately 7 heart defects per thousand births were found in children whose mothers were exposed to TCE (6 - 239 ppb) during the first trimester of pregnancy compared with 3 per thousand in children of unexposed mothers. It is not clear that the heart defects reported in this study are exclusively related to TCE exposure since dichloroethylene (DCE) was also present.
Other developmental effects in humans have been associated with VOC exposure. A preliminary study of birth outcomes conducted by ATSDR at Camp Lejeune, Onslow County, North Carolina found a decrease in birthweight and an increase in babies born small for gestational age whose mothers were exposed to TCE and other VOCs in drinking water. 40 Bove et al. found possible associations between TCE in drinking water (>5 ppb) and neural tube defects and oral clefts. This study did not, however, find an association between these low levels of TCE and increased heart defects. 41 Lagakos et al. found an association between two groupings of birth defects and exposure to VOCs in drinking water, including TCE at a maximum of 267 ppb. This study has been criticized, however, because of the improper grouping of birth defects that are not linked in fetal development. 42 Data gathered by the ATSDR TCE Subregistry indicate a potential relationship between TCE exposure and speech and hearing impairment in children 0 - 9 years of age. The subregistry data are inconclusive, however, as to the amount of TCE exposure necessary to cause such an effect. 43,44
As with most investigations of environmental exposure, the studies noted above have important limitations. One of these is the uncertainty of the exposure estimate. The amount and duration of the exposure are not clear and the exposed population is often grouped together over a wide range of doses. This lack of precision in defining how many were exposed, to how much, and for how long makes it difficult to determine a level of concern as opposed to a controlled animal study. Real-world exposure of humans to chemicals in the environment, however, is important and relevant. These studies, considered in aggregate, "suggest" an association with TCE and birth defects. More study is needed to to determine what levels of TCE in drinking water, if any, present a risk to the developing fetus.
The ability of TCE to cause cancer in humans is very controversial. The International Agency for Research on Cancer (IARC) recently classified TCE as probably carcinogenic to humans (Group 2A). 20 EPA withdrew its classification of TCE as a B2 probable human carcinogen in 1988 and will be issuing a new classification by the end of 1997. This former classification was based on sufficient evidence of cancer in animals and inadequate evidence in humans.16
High doses of TCE can cause lung and liver tumors in mice and kidney tumors in rats. Some of these animal experiments have been questioned because preservatives were used that may have contributed to the formation of these cancers. There is no clear evidence that any type of cancer has resulted from exposure of humans to TCE. Suggestive evidence indicates that workers exposed to TCE from dry cleaning operations showed an increase in lung, cervical and skin cancer. Dry cleaners also use other chemicals, however, including tetrachloroethylene (PCE) which could be responsible for this increase. Increases in leukemia were detected in two populations exposed to TCE in drinking water. Both of these populations, one located in Woburn, MA and the other in New Jersey, were also exposed to other chemicals found in the drinking water.
Cancer risk estimates made in this health assessment used a cancer potency factor derived by EPA from animal data. The relevance of cancer caused in laboratory animals at high doses for humans exposed to much lower levels found in the environment is questionable. Such animal data are considered to be much stronger when supported by evidence of cancer in humans. In many cases, as with TCE, evidence of cancer in humans comes from occupational studies in which exposure was also higher than what might be experienced by people living near hazardous waste sites. In order to relate these high dose exposures to lower environmental exposures, estimates are made using mathematical equations. These mathematical equations are used to derive a cancer potency factor that can be used to estimate risk. A discussion of cancer risk estimation is given in the introduction of the Pathways Analysis section (page 11).
Total Petroleum Hydrocarbons
Total petroleum hydrocarbons (TPH) are a group of chemicals associated with petroleum products. Most of the TPH contamination found at Fairchild is the result of jet fuel spills. The jet fuel most often used by the base is called JP-8 which contains chemicals similar to those found in gasoline. When fuel oil is spilled, the more volatile components (VOCs) will off-gas into the air. Some VOCs associated with fuel oil are known as the BTEX chemicals (benzene, toluene, ethylbenzene, and xylene) and are generally considered to be the most toxic components of fuel oil. The BTEX chemicals are also the most likely to move in groundwater and contaminate drinking water wells.
Although good toxicity data are available on the BTEX component of fuel oil, there is little data on the dozens of other hydrocarbons present. Since the BTEX component is not expected to remain in soil or surface water, exposure to old fuel spills will involve less volatile hydrocarbons. As fuel spills were transported through the base drainage system into No-Name Ditch, some of these hydrocarbons stayed in the surface water while some fell to the sediment. Over time, these chemicals break down and can no longer be detected. No TPH were detected during the most recent sampling in the ditch.
The Department of Ecology has adopted the approach of using data gathered on chemicals of similar structure to evaluate potential non-cancer effects from TPH exposure. This approach indicates that the maximum level of TPH ever detected in the off-base area of No-Name Ditch does not represent a health hazard. The only cancer-causing chemicals associated with TPH from jet fuel spills is benzene. As described above, benzene is not expected to migrate to off-base areas of the ditch and has not been detected at levels of concern in ditch sediment or surface water.
Tordon
Tordon is the trade name for the herbicide produced by the Dow Chemical Company. The active
ingredient in Tordon is picloram (4-amino-3,5,6-trichloro-2-picolinic acid) which in some
formulations is accompanied by other herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D).
Tordon is applied as a liquid or as granules to control broad-leaf weeds. Tordon has been
detected in soil up to 445 days after application and can leach to groundwater because of its poor
sorption to soil. 45
The EPA has established an RfD for picloram based on increased liver weights found in dogs fed
high doses of picloram in their diet. 16 The cancer potential of picloram is unclear. A study
conducted by the National Toxicology Program did not find any evidence of cancer in mice but
did find a significant increase of benign liver tumors in female rats fed high doses of picloram in
their diets. As with all laboratory animal studies, the doses used were extremely high compared
with what might be encountered in the environment.
West Thorpe Road area residents were exposed to picloram in drinking water and soil at very
low levels for an unknown period of time. The estimated dose received by these residents is 55
times below EPA's RfD, 10,000 times below the no-observed adverse effect level (NOAEL) and
50,000 times below the lowest observed adverse effect level (LOAEL). This comparison
indicates that residents received doses far below those that might cause a non-cancer adverse health effect.
As discussed previously, cancer risk is never zero. The cancer risk resulting from the amount of
picloram found in the West Thorpe Road area depends on the duration of the exposure. If
exposure began only shortly before the effect on nearby gardens was noticed, then the cancer risk
would be insignificant. If, however, picloram was present in residential wells and garden soil for
several years, then this risk would increase. Considering the very low levels of Tordon detected,
it is unlikely that any length of exposure would cause a significant increase in cancer risk.
Lead occurs naturally in very small amounts throughout the environment and, therefore,
everyone has some lead in their bodies. The use of lead compounds in gasoline, batteries, pipes,
ammunition and paint has contributed to the widespread dispersion of lead in air, soil, and water.
A major exposure pathway of concern is the ingestion and inhalation of indoor house dust
contaminated with lead from chipped and peeling paint. Lead in drinking water that leaches from
solder in old plumbing has also been identified as a pathway of concern. These man-made
sources of lead in the environment can increase the amount of lead in our bodies to toxic levels.
Children below six years of age are thought to be the most susceptible to both exposure and
toxicity of lead.
The non-cancer effects of lead are well known. At high doses, lead can cause severe toxicity to
the brain, known as encephalopathy. Lower doses have caused peripheral nervous system
toxicity, kidney damage, and blood disorders. The most sensitive toxic effect of lead poisoning
is believed to be impaired development of the central nervous system in children. This effect has
been measured by observing changes in the behavior of children, including performance in
school. These changes have been measured at very low levels of lead in the blood. No safe level
of lead in blood has been established for these types of effects. The EPA has set an action level
for lead in blood of 10 micrograms of lead per deciliter of blood (ug/dl). Children that exceed
this level are considered to be at risk and should have their exposure reduced.
The EPA has classified lead as a Group B2 probable human carcinogen. This classification was
based on sufficient evidence of cancer in animals and inadequate evidence in humans. Several
studies have shown that high doses of lead in laboratory animals can cause kidney tumors. 16
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