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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 effectsare discussed because there is currently no exposure occurring. The pathways are discussed interms of contaminants of concern that are present and the potential for an exposure to occurshould the pathway become complete in the future.

Pathway 1: Future Off-Base Development --> Groundwater --> Off-Base Residents

SUMMARY

Off-base areas adjacent to the Craig Road Landfill (SW-8), wastewater lagoons (WW-1) and theformer fire training area (FT-1) are currently not suitable for domestic use of groundwater. TCEdetected in off-base monitoring wells north and east of the Craig Road Landfill andeast/southeast of the wastewater lagoons are above a level of concern. Perimeter wells at theeastern border of the FT-1 site suggest that VOCs may be present in groundwater directly east ofthis site. Past detections of elevated inorganic substances (metals) at the WW-1 and FT-1 sitesare difficult to interpret. Elevated metals may be present in off-base groundwater east of theWW-1 and FT-1 sites.

BACKGROUND

The Craig Road Landfill (SW-8) has contaminated a large area of groundwater to theeast/northeast with TCE. Groundwater contamination originating from the Craig Road Landfillis 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 atMW-85 located on the northeast border of the landfill. The most recent sampling of off-basemonitoring 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 TCEand has contaminated residential drinking water wells in the West Thorpe Road area. This plumeis discussed more extensively under completed exposure pathway 2 (page 30). The maximumlevel 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 1997site detected an off-base maximum of 45 ppb TCE also at MW-120. MW-120 is an shallow welllocated approximately 800 feet east of the WW-1 site that has shown increasing levels of TCEsince initial sampling detected 18 ppb in April/May, 1991. MW-122 is a bedrock (Basalt A) welladjacent 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 chlorideand cis-1,2-dichloroethylene (cis-1,2-DCE) which are both degradation products of TCE. Themost recent sampling of off -base wells near the WW-1 site in June 1997 detected vinyl chlorideand cis-1,2-DCE at maximum levels of 2.2 and 34 ppb, respectively. The maximum levels ofthese 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) areahas reached base perimeter monitoring wells but has not impacted off-base wells 800 feet east ofFT-1. The FT-1 site is located on the east perimeter of the base just south of the wastewaterlagoons. It is a 250-foot diameter area of gravel and sand used for fire training purposes fromthe early 1970s until 1990. Prior to 1970, a nearby area of open ground was apparently used forthis purpose. Mock fires were staged 2-3 times per month by igniting about 300 gallons of cleanor water contaminated JP-4 fuel applied from a nearby 5,000 gallon underground storage tank toaircraft and building mock-ups located in the gravel area. Approximately 125 gallons of aqueousfilm-forming foam (AFFF) was used to put out each fire. The aircraft mock-up was reportedlysurrounded by a sand and gravel berm. Excess fuel, water, and AFFF were collected in a catchbasin that flowed to an oil/water separator. The separator apparently discharged to surroundingsoil. At the time of the IRP Phase I inspection in 1984, this separator did not appear to beoperating properly. Soil stained areas were noted in the vicinity. Fire training operations movedto the FT-2 site area in 1990. A bioventing and air sparging system designed to remediate bothsoil 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. TCEhas been detected at low levels at the FT-1 site but was not detected in any 1996 samplingrounds. 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-basemonitoring well MW-152 during March 1996 sampling. Benzene was found in MW-152 at 290ppb 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 atperimeter 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 sitein June 1997 detected benzene at a maximum of 91 ppb in MW-247 and vinyl chloride at amaximum of 9.1 ppb in MW-226. VOCs detected in wells at the FT-1 site are primarily in theshallow 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 areagroundwater during analysis between 1986 and 1991. The maximum levels of metals detected inon-base monitoring wells are given in Appendix C Table 7. These values are from unfilteredsamples of shallow monitoring wells and are suspect for sediment contamination. Filteredsamples 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 tosuspended solids that can travel to drinking water wells. Unfiltered bedrock samples should bean accurate measure of metals that could reach residential wells since no fraction is excluded andsediment contamination is minimal.

Analysis of the most recent unfiltered samples taken in 1991 showed much lower levels ofmetals. This result could indicate a reduced amount of sediment contamination and/or reducedlevels 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 wellMW-152. No other metals have been detected at levels of concern in off-base wells.

HEALTH ASSESSMENT

The plumes discussed above are either present in off-base groundwater or contain contaminantsat 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 CraigRoad Landfill and east/southeast of site WW-1 are above EPA's MCL. Perimeter wells sampledrecently near WW-1 also indicate the presence of cis-1,2-DCE, trans-1,2-DCE, and vinylchloride above MCLs. Installation and domestic use of groundwater wells in these areas couldresult 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 reachedmonitoring wells on the adjacent property 800 feet to the east. Groundwater at this propertycould contain vinyl chloride and benzene above levels of concern. Installation and domestic useof groundwater wells in these areas could result in exposure to VOCs in drinking water viaingestion and inhalation.

The available data for metals in groundwater at the WW-1 and FT-1 sites are difficult tointerpret. Although high levels detected in the past are apparently due to sedimentcontamination, the WW-1 and FT-1 areas could be a source for metals in groundwater. It ispossible, therefore, that groundwater east of the WW-1 and FT-1 sites is contaminated withelevated levels of metals. Installation and domestic use of groundwater wells in these areas mayresult in exposure to metals in drinking water via ingestion.

CONCLUSIONS

Groundwater in areas immediately east and north of the Craig Road Landfill (SW-8) and east ofthe wastewater lagoons (WW-1) and fire training area (FT-1) may not be suitable for domesticuse. Elevated levels of VOCs associated with these sites have been detected in nearby off-basemonitoring wells or perimeter wells. Any new drinking water wells installed in these adjacentoff-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 fromthe FT-1 and WW-1 sites.

RECOMMENDATIONS

Any new groundwater wells installed on properties adjacent to the north and east boundary ofthe Craig Road Landfill should be restricted to non-domestic uses until remedial efforts in theseareas are complete. These areas have been shown to be well within the TCE plume originatingfrom the Craig Road landfill as demonstrated from the analysis of residential and monitoringwells. Properties located in the contaminated groundwater zone include the Vietzke Villagetrailer park, Whitman College property, and the Scafco Corporation property.

Any new groundwater wells installed on properties adjacent to the east boundary of thewastewater lagoons (WW-1) and fire training area (FT-1) should be restricted to non-domesticuses until remedial efforts are complete. Shallow groundwater directly east of the WW-1 site hasshown increasing levels of TCE. Off-base monitoring wells east of the FT-1 site have not yetbeen impacted by a benzene and vinyl chloride plume extending from the FT-1 site to theperimeter of the base. This area is, however, at risk for contamination from this plume and theplume originating from the WW-1 area.

Unfiltered, low-flow samples should be taken from shallow monitoring wells (on and off-base) inthe 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

SUMMARY

Fairchild has identified thirty-nine contaminated sites on base. Current exposure of basepersonnel was evaluated above as completed exposure pathway 5. However, the potential existsfor 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 healthhazard to on-base workers could be a hazard under a residential exposure scenario. The riskposed 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 onvarious levels that should prevent the location of any new residential developments in areas ofconcern. Should the base, or any portion of the base, close in the future, any transfer of propertyis subject to the requirements of the USAF Base Realignment and Closure program that includescomprehensive environmental review.

BACKGROUND

On-base contamination of groundwater has been identified at various sites around the base. Sixof these sites are part of a Long Term Monitoring plan (LTM) because of elevated levels ofTPH, 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 theLTM, groundwater contamination has been found to a lesser degree at several other sites. Ingeneral, groundwater contamination at these sites is the result of jet fuel spills/leaks, landfills, andmaintenance shop waste discharge.

Groundwater on-base moves through both the shallow and bedrock aquifers in an easterlydirection. Of the many groundwater contamination sites located on-base, only those sites on theeastern border of the base pose any threat to off-site wells. Those sites include the Craig RoadLandfill (SW-8), wastewater lagoons (WW-1) and fire training area (FT-1) area and arediscussed in completed exposure pathways 1 and 2 and potential exposure pathway ,respectively. The widespread contamination from the many interior sites does, however, pose athreat 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 maximumvalues are given in Appendix C, Table 7.

On-base contamination of soil is discussed for Fairchild personnel under completed exposurepathway 5. The same contaminants of concern identified under this pathway exist for otherexposure scenarios should the base be redeveloped in the future. Since future development ofthe base is not predictable, a worst-case residential exposure scenario will be evaluated forexposure to contaminants of concern in groundwater and soil.

HEALTH ASSESSMENT

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 ofgroundwater for domestic purposes at these sites could result in exposure to VOCs and metals atlevels 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 currentlyunsuitable for groundwater development.

Some areas on-base may also represent unacceptable health risks through contact with soildepending on future land use. Table 4 below lists the sites that would currently be of concern forsoil 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 DescriptionContaminantsComments
FT-2Former FireTraining AreaLead
WW-1WastewaterLagoonsLead, cadmium, arsenicSediment samples.

SW-11

Former AircraftReclamation SiteLead, cadmiumSub-surface cadmiumand lead.

SD-37

UndergroundStorage TankVOCsArea of tank removalnear Building 2447

SD-38

WastewaterDrainage DitchArsenicDrainage ditches nearflight line.

It is important to note that this assessment is based on current data. Some of these sites areundergoing remediation designed to reduce groundwater and soil contamination to below a levelof concern. Conversely, some of the areas not considered to be a groundwater hazard do nothave monitoring wells in the area to confirm the absence of contamination. Also, the potentialhazard of VOC-contaminated groundwater is not restricted to use as a water supply. Dependingon various factors, including the amount and depth of contamination, VOCs in groundwater canbe a hazard through vapor infiltration directly into indoor air of homes located above acontaminated shallow aquifer. Future residential development in and around these areas shouldbe preceded by evidence showing that contaminants in soil and groundwater are below levels ofconcern.

CONCLUSIONS

Many areas on base may not be suitable for future residential development because ofgroundwater and soil contamination. The base has no plans for locating future residentialdevelopments in any of these areas. In addition, any new developments on base must undergo areview process in which the base Installation Restoration Program is a part. Any transfer ofproperty following closure of the base is subject to a comprehensive environmental review by theUSAF Base Realignment and Closure program.

RECOMMENDATIONS

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

SUMMARY

On-base supply well #2 is located at the southeast corner of the base. It supplies approximatelyone-fifth of base water needs during peak usage which occurs in the summer. Regularmonitoring of this well has shown no detections of VOCs that might be related to hazardouswaste releases. The potential exists, however, for VOCs to migrate from the nearby explosiveordnance (EOD) range.

BACKGROUND

The base is supplied with water from the Fort Wright well field located approximately 12 mileseast of the base and on-base supply well #2 located at the southern end of the base. Bothsources contribute to the base water supply with a maximum of 4,100 gal/min coming from theFort Wright well field while on-base supply well #2 contributes varying amounts with a peakoutput 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 withhazardous 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 burnand detonate explosives for an undetermined period of time. The site is located approximately2,500 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 placewithin a bermed area of the site. The site is currently used only to burn materials too unstable tobe transported off-site.

HEALTH ASSESSMENT

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 dataare available for the SW-13 area. Although soil sampling indicates that metals andnitroaromatics 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 pastburning 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 contaminationinto 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 ofexplosive ordnance does continue at the EOD range, it should be done no closer to this supply well than in the past.

CONCLUSIONS

On-base supply well #2 has not been impacted by contaminants related to any on-base hazardouswaste sites. The potential exists, however, for VOC contaminants from fuel used in the burningof ordnance at the EOD range to migrate toward this well.

RECOMMENDATIONS

No recommendations are necessary regarding the potential for contamination of on-base supplywell #2. The base currently monitors on-base supply well #2 as required for a public watersupply.

D. Toxicological Summaries

    Trichloroethylene (TCE)

Trichloroethylene (also know as trichloroethene) or TCE is a man-made chemical that exists as aclear liquid at room temperature with a sweet odor at very high concentrations in air. TCE isused primarily as an organic solvent for cleaning grease from metal parts. It is also used as asolvent in adhesives, paint removers and some household cleaning products. TCE was formerlyused as an anaesthetic and for the decaffeination of coffee. Although TCE is not a naturallyoccurring chemical, its widespread use has resulted in detectable levels in air and water all overthe world. These levels are generally higher near urban/industrial areas. An averageconcentration of TCE in the air of rural/remote areas has been estimated at 0.03 ppb.15 Levels ingroundwater 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 ofanimals. These studies have shown that rats and mice can suffer liver and kidney damage whenexposed to high doses of TCE. TCE has been shown to cause liver and lung cancer in mice andkidney cancer in rats. Exposure of the developing fetus (i.e., in utero) has been shown to causeadverse developmental effects in animals. Adverse effects on the nervous system along withchanges 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 thoseused in other studies. 39 A lowest observed adverse effect level (LOAEL) of 0.18 mg/kg-daywas calculated from this study. This LOAEL was used to compare doses estimated from theexposure of pregnant women drinking TCE-contaminated water during pregnancy. Variousother animal studies examining the non-cancer effects of long term TCE exposure in animalsshowed 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 cancause dizziness and drowsiness. Limited evidence of liver damage in workers exposed to TCEvia inhalation supports this same finding in rats and mice. Limited evidence in humans also existsto support the finding of developmental heart defects in animals. A study in Tucson, AZ, found asmall increase in heart defects of children exposed in the womb to TCE when their mothersdrank contaminated water. Approximately 7 heart defects per thousand births were found inchildren whose mothers were exposed to TCE (6 - 239 ppb) during the first trimester ofpregnancy compared with 3 per thousand in children of unexposed mothers. It is not clear thatthe heart defects reported in this study are exclusively related to TCE exposure sincedichloroethylene (DCE) was also present.

Other developmental effects in humans have been associated with VOC exposure. A preliminarystudy of birth outcomes conducted by ATSDR at Camp Lejeune, Onslow County, NorthCarolina found a decrease in birthweight and an increase in babies born small for gestational agewhose mothers were exposed to TCE and other VOCs in drinking water. 40 Bove et al. foundpossible associations between TCE in drinking water (>5 ppb) and neural tube defects and oralclefts. This study did not, however, find an association between these low levels of TCE andincreased heart defects. 41 Lagakos et al. found an association between two groupings of birthdefects 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 thatare not linked in fetal development. 42 Data gathered by the ATSDR TCE Subregistry indicate apotential relationship between TCE exposure and speech and hearing impairment in children 0 - 9years of age. The subregistry data are inconclusive, however, as to the amount of TCE exposurenecessary to cause such an effect. 43,44

As with most investigations of environmental exposure, the studies noted above have importantlimitations. One of these is the uncertainty of the exposure estimate. The amount and durationof the exposure are not clear and the exposed population is often grouped together over a widerange of doses. This lack of precision in defining how many were exposed, to how much, andfor how long makes it difficult to determine a level of concern as opposed to a controlledanimal study. Real-world exposure of humans to chemicals in the environment, however, isimportant and relevant. These studies, considered in aggregate, "suggest" an association withTCE and birth defects. More study is needed to to determine what levels of TCE in drinkingwater, if any, present a risk to the developing fetus.

The ability of TCE to cause cancer in humans is very controversial. The International Agencyfor 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 in1988 and will be issuing a new classification by the end of 1997. This former classification wasbased 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 ofthese animal experiments have been questioned because preservatives were used that may havecontributed to the formation of these cancers. There is no clear evidence that any type of cancerhas resulted from exposure of humans to TCE. Suggestive evidence indicates that workersexposed to TCE from dry cleaning operations showed an increase in lung, cervical and skincancer. Dry cleaners also use other chemicals, however, including tetrachloroethylene (PCE)which could be responsible for this increase. Increases in leukemia were detected in twopopulations exposed to TCE in drinking water. Both of these populations, one located inWoburn, MA and the other in New Jersey, were also exposed to other chemicals found in thedrinking water.

Cancer risk estimates made in this health assessment used a cancer potency factor derived byEPA from animal data. The relevance of cancer caused in laboratory animals at high doses forhumans exposed to much lower levels found in the environment is questionable. Such animaldata are considered to be much stronger when supported by evidence of cancer in humans. Inmany cases, as with TCE, evidence of cancer in humans comes from occupational studies inwhich exposure was also higher than what might be experienced by people living near hazardouswaste sites. In order to relate these high dose exposures to lower environmental exposures,estimates are made using mathematical equations. These mathematical equations are used toderive a cancer potency factor that can be used to estimate risk. A discussion of cancer riskestimation 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 petroleumproducts. Most of the TPH contamination found at Fairchild is the result of jet fuel spills. Thejet fuel most often used by the base is called JP-8 which contains chemicals similar to those foundin gasoline. When fuel oil is spilled, the more volatile components (VOCs) will off-gas into theair. 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 fueloil. The BTEX chemicals are also the most likely to move in groundwater and contaminatedrinking water wells.

Although good toxicity data are available on the BTEX component of fuel oil, there is little dataon the dozens of other hydrocarbons present. Since the BTEX component is not expected toremain 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 ofthese hydrocarbons stayed in the surface water while some fell to the sediment. Over time, thesechemicals 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 ofsimilar structure to evaluate potential non-cancer effects from TPH exposure. This approachindicates that the maximum level of TPH ever detected in the off-base area of No-Name Ditchdoes not represent a health hazard. The only cancer-causing chemicals associated with TPHfrom 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 surfacewater.

    Tordon

Tordon is the trade name for the herbicide produced by the Dow Chemical Company. The activeingredient in Tordon is picloram (4-amino-3,5,6-trichloro-2-picolinic acid) which in someformulations 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 beendetected in soil up to 445 days after application and can leach to groundwater because of its poorsorption to soil. 45

The EPA has established an RfD for picloram based on increased liver weights found in dogs fedhigh doses of picloram in their diet. 16 The cancer potential of picloram is unclear. A studyconducted by the National Toxicology Program did not find any evidence of cancer in mice butdid find a significant increase of benign liver tumors in female rats fed high doses of picloram intheir diets. As with all laboratory animal studies, the doses used were extremely high comparedwith what might be encountered in the environment.

West Thorpe Road area residents were exposed to picloram in drinking water and soil at verylow levels for an unknown period of time. The estimated dose received by these residents is 55times below EPA's RfD, 10,000 times below the no-observed adverse effect level (NOAEL) and50,000 times below the lowest observed adverse effect level (LOAEL). This comparisonindicates 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 ofpicloram found in the West Thorpe Road area depends on the duration of the exposure. Ifexposure began only shortly before the effect on nearby gardens was noticed, then the cancer riskwould be insignificant. If, however, picloram was present in residential wells and garden soil forseveral 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

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 dustcontaminated with lead from chipped and peeling paint. Lead in drinking water that leaches fromsolder in old plumbing has also been identified as a pathway of concern. These man-madesources 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 andtoxicity of lead.

The non-cancer effects of lead are well known. At high doses, lead can cause severe toxicity tothe brain, known as encephalopathy. Lower doses have caused peripheral nervous systemtoxicity, kidney damage, and blood disorders. The most sensitive toxic effect of lead poisoningis believed to be impaired development of the central nervous system in children. This effect hasbeen measured by observing changes in the behavior of children, including performance inschool. These changes have been measured at very low levels of lead in the blood. No safe levelof lead in blood has been established for these types of effects. The EPA has set an action levelfor lead in blood of 10 micrograms of lead per deciliter of blood (ug/dl). Children that exceedthis 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 wasbased on sufficient evidence of cancer in animals and inadequate evidence in humans. Severalstudies have shown that high doses of lead in laboratory animals can cause kidney tumors. 16



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