Findings
& Recommendations for the Remediation of Historic Pesticide Contamination
- Final Report March 1999
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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