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    Historic Pesticide Contamination Task Force
   
 


   
 

Findings & Recommendations for the Remediation of Historic Pesticide Contamination - Final Report March 1999
[ToC] Table of Contents

III. Human Health

A. Assessment of Human Health Risk

      A primary focus throughout the Task Force’s discussions was on the issue of risk. Several meetings were devoted to presentations about how the Department assesses and manages risks to human health in the context of the Site Remediation Program. A detailed discussion of this issue is presented below.

      In 1983, the National Research Council developed a risk assessment framework that "uses a factual base to define the health effects of exposure of individuals to hazardous materials and situations" (NRC, 1983). The Department, as do most state and federal regulatory agencies, applies risk assessment methodology to characterize health risk posed by contaminated sites throughout New Jersey. Specifically, the Department applies risk assessment methodology in accordance with N.J.S.A. 58:10B-12, which established by statute, a risk management goal of one in a million for carcinogens. This goal means that the risk presented may not result in more than one additional case of cancer in a population of one million people exposed to a certain level of a contaminant over their lifetime. In enacting this law the Legislature also created a Risk Management Commission in response to the intense technical debate over the appropriate level of risk to use as the basis for cleanup criteria. The Commission was charged with examining the scientific basis for the risk management standard of one in one million, risk assessment methodologies and evaluating their applicability for the purposes of establishing cleanup criteria. However, the Risk Commission has not completed its report. Until such time that the Risk Commission completes its recommendations and the Legislature acts to change its mandate of one in one million as New Jersey’s risk management standard, the Department is required to remediate sites to that standard.

      The growing reliance on risk assessment to make environmental decisions has led to increased scrutiny and criticism of this analytical tool. Certain commenters argue that some limitations of the method may cause exaggerated risk estimates resulting in unnecessary resource expenditures; others have argued that it may lead to underestimation of risk and impede remediation of hazardous situations. Nevertheless, risk assessment continues to be the cornerstone of environmental decision making with the understanding that there are limits to its accuracy imposed by scientific uncertainties and policy directives.

      Task force members wanted to make sure that the risks presented by soil contaminated with pesticide residues were neither overstated or understated relative to the other health risks the citizens of New Jersey contend with in their daily lives.

      Putting risk of exposure to pesticide residues in soil in context is difficult especially for the layman. Risk assessment is not an exact science. The methodologies and protocols used to evaluate risks are mathematical formulas that contain many different factors. Some factors are thought to overestimate risks and others to underestimate risk. For certain factors there is not an abundance of scientific data on which to make decisions. For example, the amount of the contaminant contained in the soil that is "available" to the human body after soil ingestion, (i.e., its bioavailability) is not well known. Bioavailability is currently a hotly debated topic (Walker and Griffin, 1998). As there is little contaminant specific bioavailability data currently available, methodologies used currently by New Jersey assume that 100 percent of the contaminant in the soil is "bioavailable."

      This is unlikely to be the case for all contaminants in all the different New Jersey soil types and so the resulting soil cleanup number affected by this factor may be conservative and may overestimate the true cancer risk. However, until additional data are gathered and evaluated, the 100 percent bioavailability factor will continue to be used. In the future, if a lower percent (less than 100 percent) bioavailability were used, the resulting standard would increase.

      Conversely, risk assessment methodologies currently use health impacts based on adult physiology. Studies have shown that children can be harmed by concentrations much lower than those that affect adults (NRC, 1993). The prescribed approach of using adult physiology to assess childhood risk results in less conservative soil cleanup criteria compared to cleanup numbers generated using sensitive populations or children’s physiology and may underestimate cancer risk.

      As the science of risk assessment improves, the public policies and technical criteria the Department uses in evaluating and mitigating risk will also improve. However, in the interim, the Department will continue to use the tools available today.

      Finally, while it is true that people voluntarily accept other risks from routine activities on a daily basis which are often greater than the risk presented by environmental exposures, this fact alone should not distract us from the goal of reducing cancer risk from environmental exposures. If decisions were based only on numerical risk, none of us would drive automobiles. Risk management decision includes many other considerations which are too involved to discuss here.

 

B. Human Health Risk and Criteria Development

      This section addresses the adverse health effects from exposure to residues of selected pesticides (arsenic, lead, DDT and dieldrin) which have historically been applied on agricultural sites. Health information for additional organochlorine pesticides is provided in Addendum 3.

      Regulatory agencies examine human and animal studies to determine the health effects of a particular contaminant. Both cancer and non-cancer health effects are examined. For arsenic, DDT and dieldrin, cancer is the most sensitive human health endpoint; for lead, non-cancer endpoints are of most concern for human health. Toxicity information alone, however, does not determine whether a person will become ill. A person must be exposed to a contaminant for a health effect to occur. In estimating exposure, a variety of default assumptions are used, including specific body weights, ages and activity patterns for people. In the context of this report, it is assumed that exposure to contaminated soil would principally occur from the ingestion of soil when children play.

      Using the combined toxicity and exposure data and risk management factor, regulators determine an allowable level of a contaminant in soil, the health-based cleanup criteria. For carcinogens, this number represents the level of a contaminant that is predicted to result in one additional cancer case occurring in a population of 1 million people exposed over their lifetimes. This one in a million additional cancer risk is the risk management factor and its use has been mandated by the New Jersey Legislature at N.J.S.A. 58:10B-12.

      While there is little debate about the need to avoid the exposure that may result in adverse effects to human health and the environment due to soil contamination, there is considerable debate on the determination of what level of protection is appropriate. For the most part, the Department uses health-based concentrations as its cleanup criteria. It should be noted, however, that the Department’s soil cleanup criteria are not adopted as regulatory standards. An effort to adopt soil cleanup criteria into regulation is currently underway.

      Even though the Department primarily uses health-based concentrations for soil cleanup criteria, the cleanup criteria for arsenic is based on natural background concentrations. For example, as discussed above, arsenic is a naturally-occurring substance. Separate from the use of any pesticide, certain soils in New Jersey have substantial concentrations of arsenic. Therefore, in considering to what level to require cleanup when there have been discharges of arsenic, the Department uses natural background for arsenic because these concentrations are typically above the health-based concentrations. For compounds that are not naturally occurring, such as DDT and its metabolites and dieldrin, the Department’s soil criteria are set at that concentration which poses acceptable risk (i.e., less than one in a million additional cancer cases).

      It should be acknowledged that there was considerable debate among members of the Task Force regarding risk assessment methodology, assumptions and models used by the Department to define human health risk. While there are considerable uncertainties inherent in the risk assessment process, it was agreed that the Task Force’s findings and recommendations would be based on the Department’s current soil cleanup criteria as listed in Table 5.

Table 5.

NJDEP Residential Soil Cleanup Criteria
for the Selected Pesticides of Concern
All criteria provided in parts per million

Arsenic 20
Lead 400
DDT 2
DDE 2
DDD 3
Aldrin 0.04
Dieldrin 0.042

      It was acknowledged that the base of scientific knowledge in the field of risk assessment will change over time and that it may be necessary to modify the findings and recommendations of the Task Force in the future.

 

C. Chemical Specific Toxicity and Soil Cleanup Criteria

1. Arsenic

      Arsenic is a human carcinogen that causes lung cancer when inhaled; and liver, lung, kidney, bladder and skin cancer when ingested in drinking water (Bates, et al., 1992). Although there is ongoing debate in the technical literature about the existence of a threshold exposure below which there is no cancer risk, the available data do not provide unquestioned support for this (Beck, et al., 1995; Carlson-Lynch, et al., 1994; Smith, et al., 1995). There has also been much debate about other issues relative to assessing risk from arsenic exposure (Mushak and Crocetti, 1995; Mushak and Crocetti, 1996; Slayton, et al., 1996). For the purposes of this evaluation, the model and strength of carcinogenicity (cancer slope factor) determined by the EPA were used (Smith, et al., 1992; Smith, et al., 1995). The non-cancer health effects, such as skin disorders including keratosis, hyperpigmentation, and vascular complications, are not considered in this evaluation because the cancer endpoint occurs at considerably lower levels than non-cancer endpoints.

      Using the EPA estimate of carcinogenic strength, the concentration of arsenic below which the cancer risk is less that one additional case in one million people exposed for a lifetime, corresponds to a lifetime exposure to a soil concentration of 0.4 ppm for residential exposure. The Department's soil cleanup criteria for arsenic (20 ppm) is based on naturally occurring background levels. Translated into cancer risk based on EPA assumptions and calculations, a person exposed to 20 ppm of arsenic has a 50 in one million chance of getting cancer over a lifetime due to arsenic exposure alone.

2. Lead

      The major health concern for lead differs from that associated with arsenic, dieldrin, and DDT. Lead has been shown to cause behavioral changes, learning disabilities and intelligence deficits (USEPA, 1998). Excessive exposure to lead causes toxic effects to the brain, kidneys and cardiovascular system. Subtle physiologic, biochemical and neurobehavioral effects are associated with lower level exposures. There is particular concern for sensitive populations, such as children and the developing fetus. While strong efforts have been and continue to be made, current scientific research indicates that acceptable concentration of lead exposure are lower than previously thought, if they exist at all (USEPA, 1998).

      The Department’s soil cleanup criteria for lead is 400 ppm for residential exposure. Unlike other criteria, this concentration is based on the results of the Integrated Exposure Uptake Biokinetic (IEUBK) model. The model is designed to assess a child’s exposure to lead in soil at concentrations that result in blood lead levels of less than 10 micrograms per deciliter of blood (ug/dL). This 10 ug/dL blood lead level is based on analyses conducted by the US Center for Disease Control that associate this and higher levels with adverse health effects in children. (USEPA, 1994)

3. DDT and Its Metabolites

      DDT is suspected of causing liver and pancreatic cancer in humans (ATSDR, 1994). Using data from human studies in conjunction with data from animal studies, the USEPA has classified DDT as a probable human carcinogen. Two structurally similar breakdown products of DDT are DDE and DDD, which also are classified as probable human carcinogens.

      Using the EPA’s estimate of carcinogenic strength, the Department’s soil cleanup criteria based on an acceptable health risk are 2 ppm for DDT, 2 ppm for DDE and 3 ppm for DDD.

4. Aldrin and Dieldrin

      In the environment and in the human body, aldrin breaks down rapidly to dieldrin. Dieldrin is a probable human carcinogen that causes liver tumors in test animals. The Department’s soil cleanup criteria based on an acceptable health risk are 0.042 ppm for dieldrin and 0.04 ppm for aldrin.

 

   
 
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