Groundwater in the Great Lakes Basin

Figure 1.
Number* of waterborne-disease outbreaks associated with drinking water by year
and etiologic agent – United States 1971-2004.
wide data reveal very few reported outbreaks of disease
related to chemicals in groundwater. There may well be
many unreported cases, especially of milder illness.
Knobeloch et al. (2000) reported on two cases of blue
baby syndrome in Wisconsin. Both babies were bottlefed.
The formula was reconstituted with water from
private wells with levels of 22.9 and 27.4 mg/L nitrate
at the time of the infants’ illness.
MMWR (1993) reported a case of blue baby syndrome
in a six-week-old girl in Wisconsin. The well water
had a concentration of 39.6 mg/L nitrate-nitrogen.
Elevated copper levels also were found in the tap water.
A reverse osmosis unit on the plumbing system failed to
reduce nitrate levels in the drinking water adequately
to prevent blue baby syndrome. The tap water was used
to reconstitute infant formula.
SURVEILLANCE AND MONITORING FOR
CHEMICALS IN GROUNDWATER
Ontario Provincial Groundwater Monitoring
Network
The Ontario Provincial Groundwater Monitoring
Network (OPGMN) is a partnership program of the
Ontario Ministry of the Environment with the local
conservation authorities and local municipalities where
there are no local conservation authorities (OPGMN,
2007). The OPGMN now has 423 wells that are located
in various areas, including contaminated sites. The
local conservation authorities or municipalities collect
water from these wells. The wells are monitored for
the ambient (baseline) groundwater quantity, flow
and quality of specific aquifers. This information helps
establish baseline conditions and assess how groundwater
is affected by land use and water use.
The OPGMN monitors groundwater for chemical
exceedences in accordance to the Ontario Drinking
Water Quality Standards (O. Reg. 169/03) under the Safe
Drinking Water Act, 2002. The program also uses the
Guidelines for Canadian Drinking Water Quality and the
Ministry Guidelines for Use at Contaminated Sites in Ontario to
determine which chemicals are of interest and may exceed
the “upper limit” (threshold value used when a chemical is
not included in O. Reg. 169/03). The information collected
is intended to help identify trends and emerging issues
and provide guidance to local decision-making authorities
in their resource management decisions. Two of the
pesticides of note that were detected from the monitoring
wells are chlorpyrifos and diazinon. The OPGMN has
reported that none of the pesticides detected are in
exceedence of the Ontario Drinking Water Quality
Standards (Grgic, personal communication).
CONCLUSIONS
Chemical contamination of groundwater is a threat to
the health of residents in the Great Lakes-St. Lawrence
River Basin. The chemicals of widespread concern are
arsenic, fluoride, radionuclides, radon, uranium and
manganese in certain geological areas, and nitrates/
nitrites and atrazine in agricultural areas where
they have been used extensively. Many chlorinated
solvents and other VOCs are a concern either because
of disposal in landfills, hazardous waste sites, spills or
leaking underground storage tanks. Trichloroethylene,
tetrachloroethylene and benzene are the most serious
concerns. Groundwater is not a major route of exposure
to pesticides, but atrazine may be the exception.
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