Exposure and Health Investigations
Exposure and health investigations of substances in the environment help to increase understanding of the risks a substance may pose to health.
Studies can involve collection of environmental and biological samples, administration of survey instruments (e.g., questionnaires or interviews), analysis and interpretation of data, and dissemination of results to study participants and others.
The summaries below provide information on studies the Site Assessment and Consultation Unit have participated with in MDH. For full reports, please contact us.
The Environmental Health Division conducts biomonitoring studies or investigations for surveillance or evaluation of policies and programs. To learn more about the studies, visit:
- Biomonitoring Study of a Tribal Community Living in the Lake Superior Basin Study
- Mercury in Newborns in the Lake Superior Basin Study
The Minnesota Biomonitoring Program measures levels of chemicals in Minnesotans and whether exposures differ between groups and over time. Visit Minnesota Biomonitoring: Chemicals in People for more information about their biomonitoring projects.
Minnesota Public Health Data Access provides facts and figures about specific chemicals in people. Visit Chemicals in people: biomonitoring to access the data.
In response to these citizen requests, MDH and the federal Agency for Toxic Substances and Disease Registry (ATSDR) conducted an Exposure Investigation in July 2008, measuring H2S gas in air at three residences near the Excel Dairy. The Minnesota Pollution Control Agency (MPCA) also monitored H2S at the Excel Dairy fenceline from May through October 2008.
In September 2008, based on the ATSDR and MPCA monitoring results, ATSDR and MDH wrote a letter to the U.S. Environmental Protection Agency and MPCA. The letter concluded that the Excel Dairy is a public health hazard and urged actions to reduce H2S emissions. In March 2009, MPCA published a Notice of Intent to Revoke and Reissue the Excel Dairy Permit. Also in March ATSDR and MDH jointly issued a full report the Exposure Investigation and MPCA monitoring results.
The site visit found that old, broken lead-acid batteries were the source of the lead poisoning. Direct exposure of the family to the lead from the batteries was unlikely, but cows’ milk was a potential route of exposure. Lead concentrations in well water samples drawn during the site visit were lower than those of previous samples and decreased with flushing. It was likely that the lead in the water was from particulates in the new well and would decrease with use or flushing. Arsenic concentrations in well water exceeded the U.S. Environmental Protection Agency (EPA) Maximum Contaminant Level at that time. The Minnesota Department of Health recommended that water from this well not be used for drinking or cooking. The arsenic in the well water was likely natural.
Treatment or alternate sources of drinking water were recommended. Blood lead samples from the residents were below levels of concern. However, there were very high levels of lead in milk from a dairy cow and it was expected that tissue concentrations from some individual cattle in this herd were also likely to be elevated above levels of concern. It was expected that blood lead levels in poisoned cattle would remain above normal concentrations. It was recommended that these cattle should be monitored individually to assure that blood lead levels are normal before meat or milk from the animals were consumed.
NEXIR was designed to examine how infants in Minnesota may be exposed to nitrate from private drinking water wells. NEXIR was a population-based study; that is, its findings characterize a cross-section of Minnesota residents who use private well water. The objectives of NEXIR were to: investigate nitrate and bacteria occurrence in drinking water among private well users; investigate history of water use, and exposure to nitrate and bacteria in young children; as related to indications of methemeglobinemia or diarrhea; assess existing knowledge among caregivers of young children about risks of nitrate exposure; and assess the need for further education for caregivers and physicians.
Preliminary analysis of water samples shows that nitrate and bacterial contamination differed between regions. Nitrate-nitrogen levels from the wellhead were over 10 mg/L in about 6% of Region I samples, and in about 23% of Region II samples. Total coliform bacteria were present in 19% of Region I samples and in about 66% of Region II samples. Fecal coliform bacteria were present in just under 1% of Region I samples and in about 17% of Region II samples. In Region I, 96% of household members drank the tap water versus 77% in Region II. Thirty percent of household members were children, with 6% below the age of 6. All participants were sent a letter with individual nitrate and bacteria results, along with MDH recommendations, within two months of their household visit.
To learn more about exposures to the community and possible health risks, MDH investigators interviewed residents living near the site. Former residents and owners of contaminated properties were also interviewed. This information, together with additional studies from Libby, Montana, has helped to identify the extent of asbestos exposure to workers and the community.
Visit Western Mineral Products to learn more about this investigation.
The goals of MARS were to: measure arsenic concentrations in private wells in areas known to have arsenic contaminated groundwater (up to 150 μg/l); develop useful geochemical, geographic, and/or geological indicators to identify Minnesota drinking water wells that are at risk of containing elevated concentrations of arsenic; determine whether people using wells that are relatively high in arsenic show evidence of exposure, as measured by elevated levels of urine and hair arsenic; and determine whether people using wells that are relatively high in arsenic show evidence of toxic effect as defined by a significant upward trend in porphyrinuria as a function of arsenic exposure.
MARS showed that most, if not all, arsenic in Minnesota drinking water comes from geologic sources. In the MARS area, the arsenic probably comes from shale brought into Minnesota by the many glaciers that crossed the state. MARS also found that arsenic is being removed from some local areas and concentrated in others. This is probably due to groundwater flow and chemical reactions. In general, well water arsenic was positively associated with hair and urine arsenic levels; individuals who had higher arsenic measurements in their hair and urine also had higher levels of arsenic in their drinking water. Urine porphyrins did not exhibit a significant relationship with water arsenic or with hair arsenic. Hair and urine may be useful biomarkers for arsenic exposure in populations. Urine porphyrin likely is not a useful biomarker for pre-clinical toxic effects of arsenic.