Groundwater in the Great Lakes Basin

isks for 23 diseases in six contiguous counties where
there were moderately elevated levels of arsenic in the
drinking water. From 1983 through 2002, arsenic levels
for 9,251 well-water samples were determined by the
Michigan Department of Environmental Quality. The
mean arsenic concentration was 11 µg/L and the population-weighted
median was 7.58 µg/L. Significantly
elevated mortality rates were found in both men and
women for all diseases of the circulatory system,
cerebrovascular diseases, diabetes and kidney diseases.
Although the ecological design of this study provides
only weak evidence for a causal association, the authors
concluded that it provides some of the first evidence
that low to moderate levels of arsenic in drinking water
may be associated with common causes of mortality.
Atrazine
McElroy et al. (2007) examined the association between
atrazine exposure and breast cancer among women
living in rural Wisconsin. Cases of breast cancer in
women 20-79 years of age incident between 1987 and
2000 were identified (n= 3,275). Female controls of
similar age were randomly selected (n= 3,669). Three
random statewide assessments of atrazine in well water
had been conducted in 1994, 1996 and 2001. These data
were used to map atrazine levels in groundwater. The
atrazine exposure for study participants was estimated
based on the combined results of the three years of
sampling. The number of wells exceeding the U.S. EPA
standard of 3 µg/L ranged from 0 to 3% in different
agricultural regions of the state. No significant association
between atrazine exposure and breast cancer was
found. This result could be a false negative because of
the small numbers who were exposed above the U.S.
EPA standard or because of the imprecision in the estimates
of actual exposure to atrazine.
Aldicarb
Fiore et al. (1986) studied 50 women ages 18 to 70
residing in Portage County, Wisconsin. Aldicarb had
been shown to be an immune suppressant in laboratory
mice. None of the study women had any known
medical reason for immune dysfunction. All used well
water as their drinking water supply. Twenty-three
had detectable levels of aldicarb in their well water.
The mean level was 16.1 µg/L; 12 in the 1-10 µg/L range
and 11 in the 11-61 µg/L range. The study found that 27
individuals drank water from a municipal well that
had not had any detectable aldicarb in the previous 4
years. T lymphocyte subsets were measured in study
participants. The exposed women had a significantly
increased absolute number of T8 cells, increased
percentage of total lymphocytes as T8 cells, decreased
percentage of total lymphocytes as T4 cells and a
decreased T4:T8 ratio. These findings are indicative of
some form of immune dysfunction. There was a statistically
significant negative correlation between the well
water concentration of aldicarb and the T4:T8 ratio.
There was also a statistically significant negative correlation
between calculated aldicarb ingestion and T4:
T8 ratio. Although this change in T4:T8 ratio was not
associated with any known clinical immunodeficiency
and its long-term implications are not known, this
study shows the potential biological impact of lowlevel
pesticide exposure in drinking water.
Mirkin et al. (1990) reported on a follow-up study of 45
of the 50 women in Portage County who participated in
the Fiore et al. (1986) study. Of these, 18 of the formerly
exposed and 27 of the formerly unexposed women took
part in the follow-up study. Only 5 of the 45 women
were currently exposed to aldicarb. These 5 women had
an increased percentage of lymphocytes in their blood
with an increased number of T8 cells. Within this small
number of exposed women there was a dose-response
relationship between aldicarb ingestion and this
increase. No contaminant other than aldicarb was found
in the drinking water that could explain these findings.
Herbicides/Fungicides
Greenlee, Arbuckle and Chou (2003) reported on a
study that looked at agricultural and residential exposures
and the risk of infertility in women. The study
examined 322 cases and controls selected from patients
at a large medical clinic in central Wisconsin. Between
1997 and 2001, women and their partners responded to
a telephone interview that assessed their state of health
and occupational and lifestyle exposures. Women who
had mixed and applied herbicides at any time two years
prior to attempting to become pregnant had significantly
reduced fertility. Mixing and applying fungicides
by either partner prior to attempting pregnancy had a
non-significantly increased risk for female infertility.
Residences using groundwater compared to municipal
water had significantly reduced infertility in women.
Nitrates
Craun, Greathouse and Gunderson (1981) reported on
a study of 102 children in Washington County, Illinois,
1-8 years old. Their well water contained 22-111 mg/L
(nitrate), at levels greater than the U.S. EPA 10 mg/L
drinking water standard. Nitrate is converted to nitrite
in the stomach. Nitrite reacts with hemoglobin in red
blood cells to produce methemoglobin. Methemoglobin
reduces the oxygen carrying capacity of the blood,
causing blue baby syndrome. None of the children had
significantly elevated methemoglobin levels and there
was no dose-response relationship between methemoglobin
and nitrate levels. This study supports the conclusion
that the known risk for blue baby syndrome from
nitrate/nitrite exposure is limited to very young infants.
Rademacher, Young and Kanarek (1992) conducted a
case-control study of Wisconsin residents who died of
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