PUBLIC HEALTH ASSESSMENT
BERTRAND CREEK AREA PROPERTIES
(a/k/a NORTH WHATCOM COUNTY GROUNDWATER CONTAMINATION)
LYNDEN, WHATCOM COUNTY, WASHINGTON
The following sections discuss exposure to the pesticides and nitrate found in north Whatcom County groundwater and the potential health effects that may result. Health effects are separated into cancer and non-cancer endpoints. Methods for assessing these types of health effects are described below.
In order to evaluate the potential for non-cancer adverse health effects that might result from exposure to contaminated media (i.e., air, water, soil, and sediment), a dose is estimated for each contaminant of concern. These doses are calculated for situations (scenarios) in which residents might come into contact with the contaminated media. The estimated dose for each contaminant under each scenario is then compared to ATSDR's minimal risk level (MRL) or EPA's oral reference dose (RfD). MRLs and RfDs are doses below which non-cancer adverse health effects are not expected to occur (so called "safe" doses). They are derived from toxic effect levels obtained from human population and laboratory animal studies. These toxic effect levels can be either the lowest observed adverse effect level (LOAEL) or a no-observed adverse effect level (NOAEL). In human or animal studies, the LOAEL is the lowest dose at which an adverse health effect is seen, while the NOAEL is the highest dose that does not result in any adverse health effects.
Because of the uncertainty in these data, the toxic effect level is divided by "safety factors" giving the lower and more protective MRL or RfD. If a dose exceeds the MRL or RfD, this indicates only the potential for adverse health effects. The magnitude of this potential can be inferred from the degree to which this value is exceeded. If the estimated exposure dose is only slightly above the MRL or RfD, then that dose will fall well below the toxic effect level. The higher the estimated dose is above the MRL or RfD, the closer it will be to the toxic effect level.
Some chemicals have the ability to cause cancer. Cancer risk is estimated by calculating a dose and multiplying it by a cancer potency factor, also known as the cancer slope factor. Some cancer potency factors are derived from human population data; others are derived from laboratory animal studies involving doses much higher than are encountered in the environment. Use of animal data require extrapolation of the cancer potency obtained from these high dose studies down to real-world exposures. This process involves much uncertainty. Current thinking suggests that there is no "safe dose" of a carcinogen and that a very small dose of a carcinogen will give a very small cancer risk. Cancer risk estimates are, therefore, not yes/no answers but measures of chance (probability). Such measures, however uncertain, are useful in determining the magnitude of a cancer threat since any level of a carcinogenic contaminant carries an associated risk. The validity of the "no safe dose" assumption for cancer-causing chemicals is not clear. Some evidence suggests that certain chemicals considered to be carcinogenic must exceed a threshold of tolerance before initiating cancer.
This document describes cancer risk qualitatively using terms like moderate, low, very low, slight and no significant increase in cancer risk. These terms can be better understood by considering the population size required for such an estimate to result in a single cancer case. For example, a low increase in cancer risk indicates an estimate in the range of one cancer case per ten thousand persons exposed over a lifetime. A very low increase might result in one cancer case per several tens of thousands exposed over a lifetime while a slight increase would require an exposed population of several hundreds of thousands to result in a single case. DOH considers cancer risk to be not significant when the estimate results in less than one cancer per one million exposed over a lifetime. The reader should note that these estimates are for excess cancers that might result in addition to those normally expected in an unexposed population.
Cancer is a common illness and its occurrence in a population increases with age. Depending on the type of cancer, a population with no known environmental exposure could be expected to have a substantial number of cancer cases. There are many different forms of cancer that result from a variety of causes. Some forms of cancer are more serious than others and not all are fatal. Approximately one quarter to one third of people living in the United States will develop cancer at some point in their lives.
Pesticides have been detected in private and public drinking water wells in the north Whatcom County area since 1984. The pesticides of concern are EDB, 1,2-DCP, DBCP and 1,2,3-TCP although other pesticides have been detected infrequently.
Routes of Exposure
The most obvious route of exposure to the pesticides of concern in drinking water is ingestion. However, the ability of these chemicals to volatilize from water makes them available for inhalation from indoor air particularly during bathing and showering. Breathing these pesticides from indoor air can contribute as much or more to the total dose than that of ingestion. Dermal absorption from water during normal household use is expected to contribute only a small fraction of the total dose. The contribution of each route of exposure to the overall dose of EDB and 1,2-DCP is illustrated in Chart 3 below.(b) It should be noted that one study measured a dermal dose of chloroform during a shower that was similar to that of inhalation, suggesting that the modeled dermal dose shown in Chart 3 may underestimate dermal exposure.20
Non-cancer adverse health effects are not expected to result from exposure to pesticides at levels found in north Whatcom County groundwater. Doses were estimated for a young child exposed through ingestion, inhalation of vapors and dermal contact to the maximum detected levels of EDB, 1,2-DCP, DBCP and 1,2,3-TCP found in drinking water (Appendix B, Table 4). None of the doses calculated for these pesticides exceed their respective MRLs or RfDs.21 Using a child exposure scenario is expected to be protective of the general population. Children are often the most sensitive population with respect to chemical exposure since they ingest more water, contact more soil and breathe more air per unit of body weight than adults. Children are also susceptible to developmental toxicity that can occur at levels of exposure much lower than those causing other types of toxicity.
An RfD or MRL was not available for EDB. Therefore, the estimated EDB dose was compared with a lowest-observed adverse effect level (LOAEL). This LOAEL is based on sperm abnormalities in bulls given high doses of EDB in their diet and is 5,600-fold higher than the EDB dose estimate.22 In other words, the lowest dose of EDB that caused any health effects in animals is still 5,600 times higher than what was calculated for a resident drinking the maximum level of EDB found in north Whatcom County drinking water. Toxicity information on each pesticide of concern is provided in the Chemical Specific Toxicity section located on page 20.
The combined effect of these pesticides was considered by adding the estimated doses. This combined dose did not exceed a "combined" RfD (also known as a hazard index). It is important to note that some chemicals can cause more than an additive effect when combined, in which case this assessment will underestimate the potential for adverse health effects. There is little evidence, however, of such synergistic effects between chemicals at levels commonly found in the environment. The potential for interactions among chemical mixtures is addressed further below.
Since pesticide levels in north Whatcom County wells are declining, using maximum concentrations detected in drinking water will overestimate current and future exposure for most if not all residents. However, pesticide levels could have been higher prior to initial testing. No information could be located with respect to when soil fumigants containing EDB and 1,2-DCP were first used in north Whatcom County. Since EDB was available in the early 1970s and 1,2-DCP in 1956, the potential exists for several years of exposure prior to initial testing.
Of the four pesticides evaluated as contaminants of concern in north Whatcom County drinking water, only EDB is currently classified by EPA as to its carcinogenicity. EDB is a Group B2 probable human carcinogen based on its ability to cause cancer in animals at high doses. These animal studies have shown EDB to be a potent carcinogen by all routes of exposure causing a wide variety of tumors including cancers of the forestomach, lung, nasal cavity, mammary glands and blood vessels of various organs. However, there is currently no evidence to show that levels commonly found in the environment can cause cancer in humans. The potential for chemicals to cause cancer in humans is often assessed by evaluating workplace exposure. Two studies of workers exposed to EDB primarily through inhalation at manufacturing plants found no statistically significant increase in mortality.22,23
Although EPA has withdrawn the cancer classification for 1,2-DCP, DBCP and 1,2,3-TCP, each of these pesticides was formerly considered a Group B2 probable human carcinogen based on long-term animal exposure studies carried out by the National Toxicology Program (NTP). As with EDB, there is no evidence that these three pesticides can cause cancer in humans although studies are limited.7,8,24 The available cancer data for these pesticides are discussed in the Chemical Specific Toxicity section located on page 19.
The relevance of cancer found in high dose laboratory animal studies 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 order to relate these high dose animal exposures to the lower environmental exposures experienced by humans, estimates are made using mathematical equations. These mathematical equations are used to derive cancer slope factors (CSFs) that are measures of cancer potency and can be used to estimate risk. Cancer risk estimates in this health assessment utilized CSFs derived by EPA from animal data. A discussion of cancer risk estimation is given in the introduction of the Public Health Implications section located on page 11.
Cancer risk estimates for each of the four pesticides noted as contaminants of concern are given in Appendix B, Table 5. These risks were estimated for long-term (i.e., 30 years) exposure of a child/adult using water contaminated with the maximum detected level of each pesticide. An evaluation of these estimates indicates that EDB at a level of 6.1 ppb carries a moderate to low increase risk of cancer. Maximum levels of the other pesticides are categorized as a low to very low increased risk of cancer.
The most recent comprehensive sampling of wells by DOH in November 1998 revealed a maximum level of EDB more than 10-fold lower than the overall maximum used above to estimate cancer risk. Only two of 22 wells sampled during this period contained detectable levels of EDB. The other pesticides of concern were also detected infrequently and at very low levels during this recent sampling. Since EDB contributes the majority of the cancer risk estimated above, it is apparent that overall cancer risk has declined significantly. However, even at the MCL, the high potency of EDB as an animal carcinogen translates into a low to very low cancer risk.
It is useful to note that the high cancer potency of EDB is attributed to the formation of forestomach tumors in rats and mice exposed by the ingestion route while potency via inhalation appears to be much lower. This discrepancy is illustrated in Chart 4 which shows the distribution of cancer risk by route of exposure. Considering this difference, the supply of bottled water to residents with EDB contaminated wells may have provided a greater reduction in cancer risk than is apparent from a simple comparison of dose and exposure route.
Many drinking water wells have only low levels of 1,2-DCP that do not pose a significant cancer risk to residents using these wells for drinking and other domestic uses. However, wells with higher levels of 1,2-DCP (e.g., > MCL) or multiple pesticides can pose a low to very low cancer risk regardless of the presence of EDB. Pesticide sampling data indicate the presence of 1,2-DCP in every sample that contained 1,2,3-TCP or DBCP.
Exposure to the levels of pesticides found in many north Whatcom County wells is considered to be below a level of health concern for both cancer an non-cancer endpoints. In addition, cancer risk associated with pesticides at levels of health concern is likely overestimated. There is no evidence that this level of pesticide exposure can cause cancer in humans. We encounter cancer risk every day from both natural and man-made carcinogens in our food, air and water. It is useful to consider these "background" exposures to better understand the relative risks associated with the pesticides in north Whatcom County drinking water wells.
Routes of Exposure
The only route of exposure considered to be significant for nitrate in drinking water is ingestion. Nitrate will not volatilize from water and the amount of dermal absorption compared to ingestion is expected to be minimal.
Ingestion of drinking water containing nitrate at or above the MCL of 10 ppm may pose a health hazard for infants due to the risk of methemoglobinemia. A risk for adverse birth outcomes also exists for pregnant women drinking water that contains nitrate above the MCL.
Nitrate varies widely in north Whatcom County drinking water wells. Of the 2,619 nitrate test results compiled by WCHHS, 122 exceeded the MCL of 10 ppm with a maximum of 56 ppm. The estimated dose of an infant ingesting 0.6 liters per day of formula prepared with drinking water containing nitrate at the MCL of 10 ppm is equivalent to the RfD for nitrate. This RfD is based on a study that found no methemoglobinemia in infants exposed to nitrate in drinking water at levels below 10 ppm while two percent of infants exposed at 11-20 ppm showed early clinical signs of this disorder. Most studies show that nitrate levels below 20 ppm will not result in symptoms or adverse health effects unless accompanied by a large dietary nitrate source or simultaneous exposure to bacteria. Bacteria in the digestive tract can enhance the conversion of nitrate to nitrite.21 A recent literature review suggests that bacterial and viral infections of the digestive system (i.e., gastroenteritis) may be the cause of many infantile methemoglobinemia formerly attributed to nitrate in drinking water.25
Nitrate-induced methemoglobinemia is caused by decreased oxygen delivered to body tissue by the blood and is directly related to the conversion of nitrate to nitrite in the body. Infants are more susceptible to nitrates in drinking water because of a relatively high fluid intake and increased levels of fetal hemoglobin compared with older children and adults. Fetal hemoglobin is more easily converted to methemoglobin than is the adult form. At very high levels of exposure, the decreased oxygen availability to the tissues can cause a serious condition called "blue baby" syndrome. This syndrome is often difficult to diagnose but is indicated by a bluish color around the lips, hands and feet. Other symptoms can include lethargy, sweating, flushed skin, vomiting and diarrhea that are easily confused with other common ailments. "Blue baby" syndrome can be diagnosed directly by measuring the amount of methemoglobin in the blood. Death can result if severe cases are not recognized and treated. 26
Some animal studies have shown a relationship between adverse birth outcomes and nitrate in drinking water but only at high doses.27 A LOAEL was derived from a study that found impaired neurobehavoiral development in rats given relatively low doses of nitrate in utero and as pups. An estimated dose for a pregnant women drinking water containing nitrate at the MCL of 10 ppm is approximately 20 fold lower than this LOAEL. This comparison suggests that nitrate at or below the MCL is not a concern for developmental effects. Such a comparison assumes dietary intake and nitrate/nitrite metabolism are similar between the rat and human.
There is some evidence that pregnant women who drink water contaminated with nitrate are at risk for adverse birth outcomes. A recent study showed that nitrate levels above 20 ppm may be associated with increased spontaneous abortions.28 Another study showed a significant increase in birth defects associated with nitrate in drinking water at 5-15 ppm.29 The latter association could not be attributed solely to nitrate exposure since other chemicals including pesticides were likely present in the drinking water. These and other studies examining the relationship between nitrate in drinking water and birth defects remain inconclusive.30,31
EPA has not classified the cancer potential of nitrate. There is evidence that the body can convert nitrite into cancer-causing nitrosamines. It has been postulated, therefore, that nitrate in drinking water could lead to increased cancer risk via conversion into nitrite and the subsequent formation of nitrosamines. Exposure of rats to nitrite in drinking water along with concurrent exposure to nitrosable amines has been shown to cause an increase in digestive tract tumors attributed to the formation of nitrosamines in the body. However, this increase was not seen in rats exposed to nitrate and nitrosable amines. In addition, no increase in tumor formation was seen in rats exposed separately to these nitrosamine precursors. Several human studies have failed to provide clear evidence to support a link between nitrate exposure and cancer.
In almost every situation of environmental exposure, there are multiple contaminants to consider. The potential exists for these chemicals to interact in the body and increase or decrease the potential for adverse health effects. The vast number of chemicals in the environment make it impossible to measure all of the possible interactions between these chemicals. Individual cancer risk estimates can be added since they are measures of probability. When estimating non-cancer risk, however, similarities must exist between the chemicals if the doses are to be added. Groups of chemicals that have similar toxic effects can be added such as volatile organic compounds (VOCs) which cause liver toxicity. Polycyclic aromatic hydrocarbons (PAHs) are another group of chemicals that can be assessed as one added dose based on similarities in chemical structure and metabolites. Although some chemicals can interact to cause a toxic effect that is greater than the added effect, there is little evidence demonstrating this at concentrations commonly found in the environment.
Some effort has been made to assess the toxicity of chemical mixtures commonly found in groundwater. One group of researchers selected a mixture of 25 chemicals that are frequently found groundwater at hazardous waste sites for administration to mice via drinking water. One study of this mixture examined effects on the immune system while the other looked for reproductive toxicity.32,33 No adverse reproductive effects were seen while some immune responses were suppressed at the higher doses. Based on previous studies, the authors concluded that these contaminants given alone at the same doses would not have shown immune suppression activity. Although this result is suggestive of potential interactions between contaminants present in drinking water, the doses used in this study were still relatively high compared to what is often found in contaminated water supplies. The relevance to the contamination found in north Whatcom County is also limited since pesticides and nitrate were not among the chemicals in this mixture.
More recent studies have examined the effects of pesticide/fertilizer mixtures commonly found in groundwater. No adverse reproductive or developmental effects were found in rats and mice given mixtures of 1,2-DCP, EDB, DBCP, nitrate and other pesticides in drinking water at levels well above the maximums detected in north Whatcom County groundwater.34 However, a 5-year study of mice given atrazine, aldicarb and nitrate in drinking water showed immune suppression responses greater than those of mice given any single agent. This finding is supportive of the immune supression noted above for a different chemical mixture. Perhaps more importantly, the drinking water contaminant concentrations used in this study were only 2-3 times higher than their respective MCLs.35
The studies noted above provide some evidence that interactions between chemicals in a mixture can result in toxicity that is not apparent from a single agent. However, the mechanisms of these interactions are poorly understood and have not been demonstrated in humans at environmentally relevant exposures. In addition, the mixtures that did elicit immune responses when given in concert did not include the pesticides of concern found in north Whatcom County groundwater. Finally, the study of chemical mixtures is in its infancy and is a recognized deficiency in the toxicological database. While there appears to be no evidence specifically associating the chemical mixtures of concern in north Whatcom County, the limited information cited above suggests that immunological endpoints could be a target of such an exposure.
Information communicated to DOH by concerned citizens indicates that some migrant farm worker camp workers and their families live year round at the camps in north Whatcom County. In addition, many camp workers are likely to work at other camps with a later crop harvest. Dose estimates for camp workers, therefore, assumed chronic, year-round exposure.
The only pesticide currently present in migrant camp wells is 1,2-DCP detected at a maximum level of 1.8 ppb in April 1999. This level of 1,2-DCP is far below the maximum found in other area drinking water wells. As noted previously, non-cancer health effects are not expected to result from exposure to the maximum levels of pesticides found in any area well. Cancer risk from exposure to the current levels of 1,2-DCP found in camp wells is not considered to be significant. Previous detections of EDB in one camp well indicated that a low or very low cancer risk existed for those workers exposed over many years to EDB in this well.
An important issue in assessing farm worker exposure is the potential for workers to contact pesticides in soil and indoor dust. Although there is no soil or dust sampling data for north Whatcom County migrant camps, previous studies have demonstrated that these exposure pathways are of concern.36,37 Workers can be exposed to pesticides in soil through incidental ingestion, dermal contact and inhalation of dust. In addition, families can be exposed in the home when contaminated soil is tracked indoors and accumulates as indoor dust. Exposure of farm workers and their families to pesticides in soil and indoor dust is dependent upon pesticide use, work habits and precautions taken by individual workers and their employers.
Nitrate has consistently been detected in migrant camp wells. Concerns for pregnant women and infants exposed to nitrate above the MCL are addressed above. Also addressed above is the potential interaction between pesticides and nitrate in drinking water. Although pesticides are at low levels in only two of the camp wells, additional exposures from soil and indoor dust could augment the pesticide dose. Interactions between the pesticides found in north Whatcom County groundwater and nitrate are not of concern for reproductive or developmental endpoints. However, recent evidence indicates a potential for adverse effects on the immune system from exposure to commonly uses pesticides and nitrate in drinking water. This finding indicates a need to further investigate the potential for adverse health effects from exposure to both nitrates and pesticides, particularly with respect to the immune system.
Ethylene dibromide (EDB or 1,2-dibromoethane) was used extensively in the past as a soil fumigant pesticide and leaded-gasoline additive. An EPA ban on EDB use as a soil fumigant in 1984 along with a decline in the use of leaded-gasoline has significantly reduced the amount of EDB used in the United States. The source of EDB in the north Whatcom County area is thought to be the result of past use as a soil fumigant.
Non-cancer adverse health effects observed following exposure to EDB are largely restricted to high-dose animal studies. Some of the primary target organs for EDB toxicity in animals include the kidney, liver and reproductive systems. However, no MRLs or RfDs have been derived from the available data. Liver and kidney effects have been documented in humans receiving acute, lethal doses but no evidence exists that chronic, low doses in humans can impact these organs. The reproductive toxicity of EDB in animals is supported by evidence of decreased sperm counts and sperm abnormalities found in exposed workers. In addition, adverse effects on sperm are documented in both animals and humans following exposure to DBCP which is structurally similar to EDB. The reproductive system appears to be the most sensitive non-cancer endpoint associated with EDB exposure. The highest level of EDB detected in north Whatcom County groundwater yields a dose that is still well below a LOAEL based on reproductive toxicity in animals.22
Cancer is the primary toxic endpoint of concern for EDB exposure. EDB is classified as a B2 probable human carcinogen by EPA based on its very high cancer potency demonstrated in high- dose animal studies. These animal studies have shown that EDB is carcinogenic by all routes of exposure (i.e., ingestion, inhalation and dermal) at both the point of contact and systemically. In addition, EDB is a potent genotoxin showing mutagenic activity in almost every test system studied. There is, however, no evidence that EDB can cause cancer in humans. As noted previously, two studies of workers exposed to EDB found no statistically significant increase in mortality. One of these studies did find an increase in mortality but had several limitations relating to exposure assessment and controlling for alternate exposures.22,23 These workers likely had considerably higher exposure to EDB than the worst-case exposure assumed for north Whatcom County residents.
The high oral CSF (a measure of cancer potency) of EDB was derived by EPA from an oral gavage study of rats that resulted in a very high frequency of forestomach tumors. Similar tumors were found in mice dosed with EDB in drinking water. A study of rats exposed to high levels of EDB in air showed various tumors of the nasal cavity from which EPA derived an inhalation CSF that is100-fold lower than for the oral route.22 It is important to note that the oral and inhalation cancer potencies are based on site contact as opposed to systemic tumors suggesting that a combined systemic dose is not appropriate for risk estimation.
One other aspect of EDB toxicity that deserves mention is the chemical interaction between EDB and disulfiram (Antabuse). Antabuse is a drug used to control alcoholism that has been shown to potentiate the toxicity of EDB in rats. Although this synergy of effect has not been seen in humans, persons using Antabuse should take extra precautions to avoid EDB exposure.
1,2-dichloropropane (1,2-DCP) has been used as a solvent, pesticide, photographic processing chemical and as an intermediate in the formation of other chemicals. The likely source of 1,2-DCP in north Whatcom county groundwater is through the past use of soil fumigant pesticides that contained 1,2-DCP as a by-product.
The primary target organs of 1,2-DCP appear to be the liver, kidney and nervous system as demonstrated by high dose oral and inhalation studies in animals. Limited case studies of humans exposed to acute doses of 1,2-DCP also describe adverse impacts on the liver and kidney. However, no evidence was located to suggest that these adverse health effects could occur at lower, more relevant chronic doses. A chronic MRL of 0.09 mg/kg-day was derived by ATSDR based on liver necrosis seen in rats following oral doses of 1,2-DCP.24 This MRL was used to compare the doses estimated for north Whatcom County residents exposed to the maximum detected level of 1,2-DCP (28.4 ppb) detected in drinking water. As shown in Appendix B, Table 4, this estimated dose, which included all routes of exposure, is about 36-fold below the MRL and 49,000-fold below the actual dose that caused liver toxicity.
EPA has developed an inhalation reference concentration (RfC) of 0.004 mg/m3 in air for 1,2-DCP that is based on increased cell growth in rat nasal mucosa following chronic high dose inhalation exposure.24 RfCs are levels of contaminants in air below which adverse health effects are not expected. Since RfCs are based on continuous exposure (i.e., 24 hours/day), they are not appropriate for comparison with a concentration estimated for a shower scenario. Attempts have been made to estimate whole-house levels of VOCs volatilizing to indoor air from all tap water uses.38 These estimates show that levels in the remainder of the house are generally 100-fold below those found in the bathroom following a shower. Taking this difference into account, the maximum concentration of 1,2-DCP predicted for general indoor air is about three-fold below the RfC and 1000-fold below the toxic effect level upon which the RfC is based.
Although EPA has removed its classification of 1,2-DCP as a B2 probable human carcinogen, there is evidence that high doses of 1,2-DCP can cause liver and possible mammary tumors in mice. No evidence was located regarding cancer endpoints and 1,2-DCP exposure in humans.24
1,2-Dibromo-3-chloropropane (DBCP) was used primarily as a soil fumigant prior to restrictions and subsequent cancellation of this use by EPA in 1985. Current use of DBCP is limited to the production of other organic chemicals. The source of DBCP in north Whatcom County groundwater is likely from its past use as a soil fumigant.
The male reproductive system is the primary non-cancer toxic endpoint of DBCP exposure. Abnormal sperm, decreased sperm counts and decreased fertility rates have been observed in workers exposed to DBCP primarily through inhalation at pesticide manufacturing facilities. Doses were not well characterized in these studies but are expected to be considerably higher than those experienced by north Whatcom County residents. No decrease in birth rate was found in a Fresno County, CA population exposed to DBCP in drinking water at levels ranging from 0.04-5.8 ppb.39
Reproductive toxicity has also been found in animals exposed to high doses of DBCP through both the inhalation and oral routes. In addition to spermatogenic effects, these animals also showed testicular atrophy indicating a more severe effect with increasing dose. High dose animal studies have also shown that DBCP can impact the liver, kidneys, blood, immune and nervous systems. There is little evidence to show that low doses of DBCP can impact these organs systems in humans. An intermediate MRL of 0.002 mg/kg-day was derived by ATSDR based on adverse effects on sperm seen in rats following oral doses of DBCP.7 This MRL was used to compare the doses estimated for north Whatcom County residents exposed to the maximum detected level DBCP (0.3 ppb) detected in drinking water. As shown in Appendix B, Table 4, this estimated dose, which included all routes of exposure, is about 100-fold below the MRL and 93,000-fold below the actual dose that caused sperm toxicity in rats.
Although EPA has removed its classification of DBCP as a B2 probable human carcinogen, there is evidence that high doses of DBCP administered to rats and mice can cause tumors in multiple organs, including the forestomach and lungs. The sites of tumor formation induced by DBCP in animals are very similar to those induced by EDB. There is no evidence that DBCP can cause cancer in humans.7 No increase in cancer mortality was found in one study of workers exposed to DBCP at a production and formulation facility.40 Also, the previously mentioned population in Fresno County, CA exposed to DBCP in drinking water did not show an elevation in leukemia or gastric cancer.
1,2,3-Tichloropropane (1,2,3-TCP) has been used as a solvent and as an intermediate in the formulation of other chemicals. The likely source of 1,2,3-TCP in north Whatcom county groundwater is through the past use of soil fumigant pesticides that contained 1,2,3-TCP as a by-product.
Toxic effects of 1,2,3-TCP exposure have not been documented in humans. High dose animal studies show effects on various organs including the liver, kidney, spleen and blood. An oral RfD of 0.006 mg/kg/day has been derived by EPA based on increased liver and kidney weight and a decrease in red blood cells following oral exposure of rats to 1,2,3-TCP.8 This RfD was used to compare the doses estimated for north Whatcom County residents exposed to the maximum detected level 1,2,3-TCP (2.4 ppb) detected in drinking water. As shown in Appendix B, Table 4, this estimated dose, which included all routes of exposure, is about 30-fold below the RfD and 62,000-fold below the actual dose that caused increased liver weight.
Although EPA has removed its classification of 1,2,3-TCP as a B2 probable human carcinogen, there is evidence that high doses of 1,2,3-TCP can cause oral, forestomach and possibly other tumors in rats and mice. No evidence was located regarding cancer endpoints and 1,2,3-TCP exposure in humans.8
A survey of leukemia rates in the north Whatcom County area was conducted by DOH and WCHHS.19 The survey was initiated because of a perceived increase in the childhood leukemia rate that was confirmed upon comparison with statewide cancer registry data. The survey examined the possible relationship between identified leukemia cases and pesticides in drinking water. A total of nine cases were identified with questionnaires sent out to six of these families. One of these six cases was not in the area of concern. Based on examination of drinking water data for the five households with cases in the area of concern, no association was found between pesticides in drinking water and the leukemia. The survey concludes that the presence of 1,2-DCP and EDB in drinking water was not a shared risk factor among the children with leukemia.
It is important to note that leukemia was not one of the cancer endpoints found in the high-dose animal studies that provide evidence of many other types of cancers caused by these pesticides. While there is no evidence associating any of these pesticides with cancer in humans, these animals studies provide useful information on the types of cancer that are of concern. One such cancer endpoint is the stomach, which was analyzed in a study of persons exposed to DBCP in drinking water in Fresno County, CA. No increase in gastric (stomach) cancer incidence or mortality was found in this population.39 DBCP is structurally similar to EDB and causes similar type of tumors in animals including stomach cancer. Levels of DBCP in Fresno County drinking water were similar to the EDB levels found in north Whatcom County. Studies of workers exposed to EDB and DBCP at pesticide manufacturing plants have also failed to find increased rates of cancer or mortality. It should be recognized, however, that these studies are limited by the small number of workers exposed.
While the limited human studies noted above show that low levels of these pesticides in groundwater will not result in a detectable increase in cancer within an exposed population, they do not rule out such a possibility. One major problem associated with investigating small exposed populations is that increases in cancer rates must be very high for them to be detected by epidemiological methods. Any future analysis of cancer rates associated with exposure to pesticides in north Whatcom County groundwater will have to include other exposed populations in order to enhance the statistical power to the study.
The following community health concerns were gathered from phone calls and one-on-one interviews with residents during an open house meeting at the Lynden Community Center on March 30, 1999. The questions and comments received by DOH are listed below by category and followed by a response. Many of the questions deal directly with issues evaluated in this health assessment and so the reader is referred to appropriate sections of the document.
1. I have read that EDB causes cancer or leukemia. My well at home has 1,2-DCP over safe levels and my family still uses the water for bathing and showering. My grandmother used to live in the same house without bottled water and died of cancer. Could the water have been the cause?
There is no evidence that EDB causes leukemia. There is also no evidence to show that EDB has caused cancer in humans. However, EDB and other pesticides found in north Whatcom County drinking water have been shown to be carcinogenic in animals at very high doses. The levels of EDB, 1,2-DCP and other pesticides found in north Whatcom County drinking water do represent an increased cancer risk depending on type of pesticide, concentration, exposure frequency and exposure duration. Please see the Public Health Implications section starting on page 12 for a further discussion on pesticides and cancer.
2. My gamma-GT count is 95 and my doctor told me that a normal level is 32. Alcohol is not the culprit. Does a high gamma-GT count have anything to do with exposure to these pesticides?
Gamma-GT or -glutamyltranspeptidase or GGT is a liver enzyme that is activated by liver damage. Increased GGT activity is not specific to the agents or mechanisms that can cause this damage but is a response to a general toxic effect on the liver. Since these pesticides can cause liver toxicity at high doses, it is possible that your GGT increase is related to pesticide exposure. It is not possible to determine by GGT levels alone whether any real liver damage has occurred and what might have been the cause. You should follow the advice of your physician with respect to this clinical test result. Please call Robert Duff toll-free at 1-877-485-7316 or 360-236-3371 if you would like information on physicians in your area who specialize in environmental health.
3. Will grandchildren be at risk from occasional visits?
There are no acute or short-term exposure risks associated with the levels of pesticides found in north Whatcom County groundwater. However, high levels of nitrate exposure in drinking water over a period of weeks, as opposed to years, can pose a threat to the developing fetus and infants.
Non-cancer adverse health effects are not expected from long-term, daily exposure of young children to any level of pesticide found in north Whatcom County drinking water. The low-level cancer risks described in this health assessment are estimates based on daily exposure over a 30-year period to the maximum levels of pesticide detected in area wells. Long-term cancer risk from exposure of your grandchildren over several years of visits will be considerably lower than what is assumed in this assessment. However, some cancer risk does exist depending on type of pesticide, concentration, exposure frequency and exposure duration.
Drinking bottled water is an effective way to reduce exposure to both pesticides and nitrate. However, if there are pesticides in your water, a filtration system may also be necessary to reduce inhalation and dermal exposure. Filtration methods range from simply installing a carbon filter on your shower-head to a point-of-entry (POE) system that treats all water entering your home. Ecology is currently evaluating alternative water options for the area around Bertrand Creek that could involve your home. For information on Ecology's alternative water evaluation, contact Ecology at 360-738-6250. For information on water treatment systems for your home, call the WCHHS at 360-676-6724.
4. Will inhalation of these compounds cause ear, nose and throat problems?
The pesticides found in area groundwater are volatile and can be inhaled as they volatilize from water during showering, clothes/dish washing and other household uses. At much higher air levels than would result from levels found in area drinking water, 1,2-DCP caused increased cell growth in the nasal mucosa of rats while EDB administered to mice in air caused nasal epithelial tumors. As noted in this health assessment, non-cancer adverse health effects are not anticipated from exposure to even the highest pesticide levels detected. However, some cancer risk is associated with exposure to pesticides found in north Whatcom County drinking water depending on type of pesticide, concentration, exposure frequency and exposure duration. This cancer risk is evaluated in the Public Health Implications section starting on page 12.
5. Concern was expressed about high cancer rates in the area.
A survey of childhood leukemia cases in north Whatcom County drinking water was released by WCHHS and DOH in July, 1999. No association between drinking water and elevated leukemia rates was found. However, leukemia is not one of the cancer endpoints that has been associated with the pesticides of concern in area groundwater. This study and other issues associated with measuring cancer in the area are discussed in the Health Outcome Data section on page 24.
6. How can I reduce my risk?
Water treatment systems and drinking bottled water are effective in reducing exposure to pesticides and nitrate in drinking water. It is important to consider both of these options if you have pesticide in your water since you can be exposed through drinking, breathing of vapors and dermal absorption. Ingestion and inhalation during showering/bathing appear to contribute the most to your overall dose. For information on Ecology's alternative water evaluation, contact Ecology at 360-738-6250. For information on water treatment systems for your home, call the WCHHS at 360-676-6724.
7. My 15-year-old daughter may have developed chronic fatigue syndrome. Is it related to the water?
No evidence was located associating nitrates and pesticides with chronic fatigue syndrome. You should consult with you physician for advice about diagnosis and treatment of this condition.
8. What are these contaminants doing to our bodies?
Please read the Public Health Implications section of this health assessment starting on page 12.
9. What are the risks from current pesticide applications?
This document evaluated exposure to contaminants in groundwater that likely resulted from past application of pesticides. A profile of pesticides currently applied on raspberry fields (the predominant crop in the north Whatcom County) is provided in Appendix E. Any health risk associated with use of these pesticides is obviously dependant upon exposure. Two possible routes of exposure for residents living near a pesticide-treated filed are via a contaminated drinking water well or drift from a spraying application. Drift is dependant upon several factors including type of application, type of pesticide and weather. Aerial applications are generally the biggest concern for drift. Growers are required to follow label requirements and WSDA regulations that are in place to limit pesticide drift.
Several factors play a role in determining whether a pesticide applied on a field will be a threat to a drinking water well. Among these factors are type of pesticide application (i.e., soil versus foliar), chemical physical properties of the pesticide, amount applied, frequency of application, movement of groundwater, location of drinking water wells and type of aquifer. If you are concerned about pesticides in your well and how to test for them or pesticide exposure in general, please contact the WCHHS at 360-676-6724 or DOH toll-free at 877-485-7316.
10. Can EDB cause muscle aches?
Since most of the toxicological data on EDB is based on animal studies there is no data available for this type of endpoint. The major target organs for EDB toxicity are discussed in the Chemical Specific Toxicity section starting on page 20.
11. How would I know if my health problems are related to EDB?
It is very difficult to associate health effects with chemical exposures. Such associations are usually made when the effect is very unusual and specific to a particular exposure. EDB toxicity is discussed in the Chemical Specific Toxicity section starting on page 20. As noted in this section, the doses at which adverse health effects have been noted in animals are far above those associated with the exposures experienced by north Whatcom County residents.
12. Will one year of exposure at this level be significant?
Non-cancer adverse health effects are not expected from long-term exposure to pesticides in drinking water. Nitrate exposure of pregnant women and infants over shorter time periods does represent a risk for adverse birth outcomes and methemoglobinemia, respectively.
The cancer risk from a one-year exposure of a young child to the pesticides found in drinking water will pose a cancer risk that is 30-fold below the risk estimated under the worst-case scenario presented in the Public Health Implications section starting on page 12. Generally, the shorter the duration of exposure the lower the cancer risk.
13. How can I have my well tested? Why have wells nearby been tested and not mine?
Many wells have been sampled by various agencies for different contaminants. If your well has not been tested, there is a possibility that it will be in the future but you should assume that the responsibility is your own. There is no clearly defined area of groundwater contamination. Wells that are in areas downgradient from former agricultural lands could be at risk for contamination. The nature of this risk will depend upon the type of agricultural use. For example, berry fields present since the early 1980s could be a source of the pesticide contaminants discussed in this health assessment. Dairy farms, however, are a concern primarily for nitrate and coliform.
The WCHHS has information on past and present agricultural land use as well information on certified laboratories that test for the various contaminants of concern. WCHHS can be contacted at 360-676-6724.
14. A renter wants information prior to 1990 about testing of his well. 1,2-DCP was detected at 2.6 ppb in 1990.
If your well sampling results were reported to the WCHHS, you can obtain these from WCHHS at 360-676-6724. Otherwise, you will need to get the information from whoever requested the test.
15. How can we find out about contamination in a well that serves a house we intend to buy?
You should always inquire about the water quality of a well serving a house that you intend to buy. Real estate agents should have information regarding the disclosure requirements of real estate transactions. If you are inquiring about a well in the north Whatcom County area, the WCHHS (360-676-6724) may have test results available. At a minimum, the well should be tested for nitrate and bacteria. If the well is in an area of concern for pesticides (see Figures 2,6 and 7), DOH recommends that the well be tested for EDB, 1,2-DCP, DBCP and 1,2,3-TCP.
The WCHHS has information on past and present agricultural land use as well information on certified laboratories that test for the various contaminants of concern. WCHHS can be contacted at 360-676-6724.
16. What sampling has been done on the City of Lynden's water?
The City of Lynden obtains it water from the Nooksack River and is required to regularly sample and analyze their water supply for a large number of contaminants including the contaminants of concern discussed in this health assessment (i.e., nitrate, EDB, 1,2,-DCP, DBCP and 1,2,3-TCP). None of the pesticides of concern have ever been detected in the City of Lynden or the City of Ferndale water supplies. The most recent sampling of these municipal water supplies was in April 1999. The significant dilution of these pesticides in groundwater after discharge into the Nooksack River, along with their volatile nature, makes it unlikely that they will be detected in water supplies drawing from the river.
17. Who will be sampling in the future?
There may be additional sampling of wells in the area by government agencies. However, well owners should not assume that their well will be sampled in the future. Since there is no clearly defined area of groundwater contamination, well owners need to assess land use around their wells to determine if there is an upgradient source of contamination. Wells that are in areas downgradient from former agricultural lands could be at risk for contamination. The nature of this risk will depend upon the type of agricultural use. For example, berry fields present since the early 1980s could be a source of the pesticide contaminants discussed in this health assessment. Dairy farms, however, are a concern primarily for nitrate and coliform. The WCHHS has information on past and present agricultural land use as well as information on certified laboratories that test for the various contaminants of concern. WCHHS can be contacted at 360-676-6724.
18. A resident expressed concern about past exposure of her two daughters who lived at Mallards Landing from 1980-1991. How can we know if our well was contaminated?
No sampling data were located for the former well at Mallards Landing. According to DOH public drinking water records, this water system has been inactive since August 1979. Century Water Association currently supplies drinking water to Mallard's Landing. This source is listed as being active since February 1980. Periodic testing of this water supply since 1992 has not detected any of the pesticides associated with groundwater contamination in the area. However, no data were located for this system prior to 1992. For more information on the drinking water supply that served residences at Mallards Landing please contact the WCHHS at 360-676-6724.
19. Will filters work? Is carbon filtration of drinking water effective?
Carbon filtration devices installed on shower heads demonstrated greater than 99 percent effectiveness at removing both EDB and 1,2-DCP from shower water. The effectiveness of one brand of filter over time was previously evaluated for removal of EDB at concentrations of about 2 ppb. Removal efficiencies remained greater than 99 percent until the 12th month when a slight detection of EDB was made corresponding to a 98.9 percent removal efficiency. WCHHS is currently evaluating such a device over a several month period to determine removal efficiencies of 1,2-DCP over time (see Table 3, page 11). In addition, ATSDR measured 1,2-DCP levels in air before and after carbon filtration of shower water and found good removal efficiencies from shower water along with a 95 percent decline in bathroom air levels. These data show that shower filters are effective at removing both EDB and 1,2-DCP.
These devices can, however, be fouled by high mineral concentrations associated with water hardness. In addition, carbon filters can accumulate bacteria after extended use which can then discharge into the water stream. Carbon filtration devices will need to be replaced regularly and more frequently if hard water fouling is evident. It is also important to remember that filters will not remove nitrate. Reverse osmosis treatment systems can do this but are more expensive to both purchase and maintain.
Filtration methods range from simply installing a carbon filter on your shower-head to a point-of-entry (POE) system that treats all water entering your home. Ecology is currently evaluating alternative water options for the area around Bertrand Creek that could involve your home. Information on Ecology's alternative water evaluation and water treatment systems for your home is available at WCHHS (360-676-6724).
20. Will someone test my filtered water to see if the 1,2-DCP detected at 3 ppb is being removed?
The WCHHS has information on certified laboratories that test for the various contaminants of concern and can be contacted at 360-676-6724. Carbon filtration devices can remove more than 99 percent of 1,2-DCP from your water. WCHHS is currently evaluating the effectiveness of these filters over time (see Table 3, page 11). It is important to note that these filters need to be changed according to manufacturer specifications and possibly sooner if the filter is being fouled by high water hardness.
21. Concern was expressed about nitrate and high pH in water served by the Delta Water Association. The association has a notice out that "babies should not drink the water." Concern was also expressed about EDB in this water.
The reason for the notice about babies not drinking water from this system is that it contains nitrate above the maximum contaminant level (MCL) of 10 ppm. The most recent sampling of this water system in April 1999 detected nitrate at 15.9 ppm. Infants could experience a condition known as methemoglobinemia if fed formula that is mixed with water containing nitrate above the MCL. Pregnant women should not drink this water due to the risk of adverse birth outcomes. For more information regarding nitrate toxicity, see page 16 of the Public Health Implications section of this document.
EDB has not been detected in four samples taken from the Delta Water Association water system between 1992 and 1994. Regular VOC sampling of this system has shown no detections of any pesticide associated with north Whatcom County groundwater contamination.
22. What are the levels of nitrates to be concerned about?
The federal limit for nitrate in public water systems, known as the MCL, is 10 ppm. DOH has adopted this standard and considers it to be health protective. For information regarding nitrate toxicity, see page 16 of the Public Health Implications section of this document.
23. A resident expressed concern about the use of manure as fertilizer on a nearby berry field and increasing nitrate concentrations in his well.
Unfortunately, this is not surprising in agricultural areas where shallow wells are located. Many of the wells in the north Whatcom County area have nitrate problems. If the source of the nitrate, whether manure or other fertilizer, continues to be applied upgradient of your well at the same rate, your nitrate problems will likely continue. Bottled water is an effective remedy since ingestion is the only route of exposure that poses a health concern. There are also treatment systems available that will remove nitrate from your water. These systems are expensive to purchase and maintain, however. For information regarding nitrate toxicity, see page 17 of the Public Health Implications section of this document. Information on water treatment systems for your home is available at the WCHHS (360-676-6724).
24. Will nitrate at 12 ppm affect my grandchildren?
It is unlikely that nitrate at this level will affect your grandchildren unless they are infants less than one year of age. However, this level of nitrate is above the MCL and is considered unsafe for infant formula preparation as well as pregnant women. For information regarding nitrate toxicity, see page 17 of the Public Health Implications section of this document.
25. Migrant farm workers do not know if their water is contaminated and are not being informed. Notices are not getting to workers. Bottled water is not being supplied.
DOH and WCHHS have distributed fact sheets to the community in both English and Spanish. This fact sheet explains the results of a DOH assessment of drinking water contamination in the north Whatcom County area.
The necessity of drinking bottled water is dependant upon the nitrate contamination in drinking water supplied to migrant farm worker camps. Pregnant women and infants should not drink water at or above the MCL of 10 ppm. However, showering, bathing and other household uses of water are not of concern. For information regarding nitrate toxicity, see page 16 of the Public Health Implications section of this document.
26. Workers and families are experiencing asthma, headaches, skin lesions, cancer and trauma. Life expectancy is low for farm workers.
Adverse health effects are not anticipated to result from current exposure of north Whatcom County migrant camp workers to contaminants in drinking water. However, past exposure of workers and families over many years to EDB in the Ehlers camp well does carry a low to very low cancer risk. The additional exposure of workers and families to pesticides in soil and indoor dust is also of concern. However, it is unknown whether the symptoms noted in your question or the reduced life expectancy are associated with farm worker exposure. Exposure associated with farm workers is discussed further on page 20 of the Public Health Implications section.
27. What are the effects of exposure to nitrate and pesticides together? Is additional exposure from working in the fields considered for both children and adults?
Exposure to chemical mixtures including pesticides and nitrates is addressed on page 18 in the Public Health Implications section of this document. Exposures specific to migrant farm workers are also addressed in this section on page 20.
28. The assumption that farm workers are not exposed year-round to contaminated drinking water is not accurate. Many families stay year round on the farm as renters or managers.
This health assessment assumed that migrant farm workers and their families live year round at farm worker camps. While this assumption is likely overprotective, information gathered from the community by DOH suggests that some families do stay at the camps year round. In addition, many workers and their families move onto other camps where further exposure to pesticides in soil and indoor dust is possible. Health issues specific to migrant camp workers are addressed on page 20 in the Public Health Implications section of this document.
How am I being exposed?
29. Is bathing harmful to me or my family?
As discussed in the Public Health Implications section on page 12, inhalation of pesticides during bathing and showering is estimated to contribute about half of the total exposure. Dermal absorption is estimated to be minimal but does contribute to the overall dose. The only exposure route of concern for nitrate is ingestion.
30. Are these pesticides in my clothing/laundry?
No. Exposure to pesticides in clothing as a result of washing with contaminated water is not a pathway of concern. These pesticides will either volatilize or remain in the water. Clothes washing could contribute to the overall inhaled dose but the major exposure from this route is estimated to be from showering/bathing.
31. Will irrigation with pesticide contaminated water leave residue on the crops? Will cooking with this water contaminate vegetables?
No. These pesticides will either volatilize from irrigation water or move back into groundwater. Cooking with water contaminated with these pesticides is expected to result in nearly complete loss to air. These pesticides can be inhaled from indoor air after water use such as cooking but this dose is not expected to be significant when compared with the inhaled dose received from showering/bathing.
32. Can you be exposed from pressurized, low-flow toilets?
There may be some volatilization of pesticides from toilets during flushing and from standing water. This potential source of inhalation exposure has not been quantified but is expected to be minimal compared to the estimated dose inhaled during a shower.
33. Can these pesticides accumulate in dairy cows?
These pesticides are not expected to accumulate in plants or animals.
34. Can contaminants in water affect garden plants?
The pesticides found in north Whatcom County groundwater will not damage garden plants. These pesticides do not accumulate in plants and will tend to volatilize during watering. Nitrate is the primary component of fertilizer and will either enhance or do nothing to your plants.
35. Why were vapors not addressed previously?
It is not clear why the potential for inhalation was not addressed earlier. Regardless of the reason, it is clear now and has been for several years that inhalation of volatile chemicals in drinking water is an exposure route of concern.
36. What is the exposure from washing dishes?
The pesticides of concern in area groundwater can volatilize during normal household water uses such as washing dishes. Therefore, pesticides could be inhaled and absorbed through the skin during this activity. While dermal absorption is not considered to be significant for this activity, it is not clear what the inhaled dose might be. Most of the available literature considers inhalation exposure during showering to be the largest percentage of the overall inhaled dose. Nitrate exposure via the inhalation and dermal routes is not of concern.
37. What is the cause of blue staining in my bathtub, sinks and water lines?
This is likely the result of soft water (low pH) running through copper pipes. The copper can leach from the pipes as copper chloride or copper sulfate which are both noted for their blue-green color.
38. Is the Nooksack River contaminated? The river should be tested.
The Nooksack River has been tested indirectly by the Cities of Lynden and Ferndale who draw their water supplies from the river. None of the pesticides of concern in area groundwater have ever been detected in either of these municipal supplies.
In addition, EPA sampled surface water along Bertrand Creek in September 1998 and found no pesticides. Contaminated water is expected to discharge to the Nooksack and other tributaries. However, pesticide levels in the river are expected to remain below a level of human health concern due the relatively low levels of these pesticides in groundwater along with the dilution effect of the river.
39. In which direction is groundwater moving? How does groundwater move over time?
In the area surrounding the City of Lynden, groundwater is generally moving at 20-300 feet/year in the direction of the Nooksack River and its tributaries. Seasonal variation does occur with respect to groundwater flow and height of the aquifer (i.e., water table).
40. Why are homes allowed to be built, bought and sold?
DOH does not regulate the sale and purchase of homes regardless of the presence of contamination on the property. You should contact local permitting authorities for the County or a real estate agent regarding the requirements relative to disclosure of environmental contamination during a real estate transaction.
41. More information should be supplied to the community.
WCHHS, DOH, Ecology and EPA have supplied several fact sheets to the community. All of these agencies strive to keep the public informed about the environmental issues affecting residents in the area. Please feel free to call Robert Duff (DOH) toll-free at 1-877-485-7316 or 360-236-3371 if you have any further questions or concerns about the groundwater contamination in north Whatcom County.
42. If my well pumped out large amounts of water would contaminant levels go down?
Probably not and, in fact, they could go up. The main difficulty in assessing the groundwater contamination in north Whatcom County is the fact that a source has not been identified. It appears that the pesticides in groundwater are the result of past use of soil fumigants in several areas. If your well is at the leading edge of a contaminant plume, then increased pumping could draw higher levels into your well. Natural degradation of these pesticides will remove them from the groundwater but this process can take many years. Nitrate levels in your well may change seasonally but will persist if the source persists. The likely source in an agricultural area like north Whatcom County is manure and other fertilizer but septic tanks are also a common source.
43. How can contaminants be removed from a well if they continue to flow in?
Natural degradation will slowly remove the pesticides found in north Whatcom County groundwater. Realistically, there is nothing you can do to prevent contaminants from entering a well if it is drawing water from a contamination zone. However, there are treatment systems that can remove nitrate and pesticides from your well before the water enters your house or at the tap. Different contaminants require different treatment systems that can be costly to maintain. DOH recommends that you evaluate all your options prior to selecting a treatment system. You can contact WCHHS at 360-676-6724 for more information on treatment systems.
Ecology is currently providing bottled water and carbon filtration units that fit on shower heads for those home with EDB or 1,2-DCP above the MCL. In addition, an assessment of various long-term solutions is underway.
44. What are the pesticide reporting requirements for growers?
Pesticide applicators are required to keep records of what they apply and make them available upon request to the Washington State Department of Agriculture (WSDA). However, these are not public records. House Bill 2741, which is currently before the State of Washington legislature, calls for a pesticide use tracking system to be established that will make pesticide use information readily available to the public. Appendix E contains information regarding pesticide use on red raspberries (the predominant crop in north Whatcom County).
b Inhalation dose calculated using a modeled bathroom air concentration following a shower. The modeled air level for 1,2-DCP agreed quite well with actual measurements made by ATSDR at two homes with 1,2-DCP contaminated wells. Inhaled dose could actually be higher due to sources other than showering/bathing.