Health effects associated with ingestion of nitrate-contaminated water have included methemoglobinemia (i.e., blue baby syndrome) in infants (1) and spontaneous abortions in laboratory animals and livestock (2,3); however, only one study in humans has reported an association between increased methemoglobin levels and spontaneous abortion (4). During March 1993, the LaGrange County (Indiana) Health Department (LCHD) identified three women who reported a total of six spontaneous abortions during 1991-1993 and who resided in proximity to each other; each had obtained drinking water from nitrate-contaminated private wells in LaGrange County (1995 population: 29,350). LCHD was subsequently notified about a fourth woman from another part of the county who had had two spontaneous abortions after she had moved into a new home with a nitrate-contaminated private well. This report summarizes the investigations of these reports by LCHD, which indicate the need for further assessment of a possible relation between ingesting nitrate-contaminated water and spontaneous abortion.

Investigation 1

Patient 1. During May 1991 December 1992, a 35-year-old woman had four consecutive spontaneous abortions: the first three at 8 weeks' gestation, and the fourth at 11 weeks. Karyotyping of one fetus did not identify a genetic explanation for the spontaneous abortion. During the investigation of this case, a neighbor was identified who also had reported a spontaneous abortion (patient 2).

Patient 2. During March 1993, a 37-year-old woman who resided one half mile from patient 1 had spontaneous abortion of her second pregnancy at 8 weeks' gestation. Her first pregnancy (which occurred at age 34, before moving to the current home) had resulted in the birth of a full-term, live-born infant. During the investigation of patients 1 and 2, another neighbor reported to LCHD a history of a recent spontaneous abortion (patient 3).

Patient 3. During July 1993, a 20-year-old woman who resided approximately 1 mile from patient 1 had spontaneous abortion of her first pregnancy during the 8th week of gestation.

Environmental Investigation

To determine possible causes of this cluster of spontaneous abortions in the three women, LCHD conducted an environmental investigation during June-September 1993. A well located on a hog farm in the vicinity of the residences of patients 1-3 had been documented to be nitrate contaminated (>50 mg/L) in 1989; LCHD had been notified about this contamination in 1990. Because of the proximity of the residences of patients 1-3 and the hog-confinement facility, persons in all 19 residences within 3 miles down gradient (i.e., the direction the groundwater was moving) of the hog-confinement facility were interviewed regarding illness and reproductive histories. Nine women of childbearing age lived in these residences, including the three patients whose spontaneous abortions had been investigated by LCHD. Five other women each reported having a full-term birth during the preceding 2 years. Water samples from the 19 wells serving the residences were tested for bacteria and nitrates. For patients 2 and 3, water samples also were analyzed for volatile and semivolatile compounds, pesticides, metals, inorganic compounds, and coliform bacteria.

Nitrate was the only contaminant in well water present at elevated levels. In the wells serving the households of patients 1-3, nitrate levels were 19.0 mg/L, 26.0 mg/L, and 19.2 mg/L, respectively (Environmental Protection Agency {EPA} maximum contaminant level {MCL} for nitrate: 10.0 mg/L). In comparison, for the five households in which women reported giving birth to full-term, live-born infants, drinking water nitrate levels ranged from 1.6 mg/L to 8.4 mg/L (mean: 3.1 mg/L).

An LCHD investigation of potential sources of nitrate contamination of the household wells indicated that the probable source of groundwater contamination was animal waste from the hog-confinement facility. This facility was located approximately one half mile from the residence of patient 1, 1 mile from patient 2, three fourths mile from patient 3, and approximately 2 miles from the residences of women reporting full-term births.

Investigation 2

After completing the investigations of patients 1-3, LCHD investigated a fourth case of spontaneous abortion in a 35-year-old woman who lived approximately 10 miles from the other three women. She had had five live births during 1984-1992. The woman's doctor reported to LCHD that she had had two spontaneous abortions during April and August 1994, both at 8 weeks' gestation: the first occurred 24 months after the birth of her fifth child and 44 months after beginning use of a new well. A mean nitrate-N level of 28.7 mg/L was detected in water samples collected during August 1994 from the household's well, which had been used since 1990. A nitrate-N level of 1.2 mg/L was detected in a second well on the property, approximately 100 feet from the first well; this well had been the source of the woman's drinking water during her first four pregnancies. Nitrate-N levels of <1.5 mg/L were present in water samples in six other wells located up gradient from the family's well and within 1 mile of the household. The only nitrate source identified near the contaminated well was the family's septic system, which was installed in sandy soil approximately 70 feet up gradient from the contaminated well. Although the well probably became contaminated by effluent from the septic tank, it is unknown when contamination occurred.

Following these investigations, all four women changed to nitrate-free sources of drinking water (i.e., bottled or reverse-osmosis treated). Subsequently, each delivered one or more full-term, live-born infants.

Reported by: W Grant, LaGrange County Health Dept, LaGrange; G Steele, DrPH, State Epidemiologist, Indiana State Dept of Health; SA Isiorho, PhD, Dept of Geosciences, Indiana-Purdue Univ, Ft. Wayne, Indiana. Div of Parasitic Diseases, National Center for Infectious Diseases; Div of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion; Div of Birth Defects and Developmental Disabilities and Div of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC.

Editorial Note

Editorial Note: The most widely recognized health problem associated with ingestion of nitrate-contaminated water is infant methemoglobinemia, and the EPA standard for nitrate in drinking water of 10 mg/L was established in 1977 to prevent this condition. Although the findings from studies of the influence of nitrate on the reproductive outcomes of laboratory animals and livestock have not been consistent, some studies have suggested a relation between nitrate consumption and spontaneous abortions (2,3). Epidemiologic studies of humans have suggested a possible relation between ingestion of drinking water containing elevated nitrate levels and an increased risk for neural tube defects (5,6) and, based on the findings of one study, a possible relation between methemoglobin levels in women during early pregnancy and subsequent spontaneous abortions (7).

An estimated 13.8 million households in the United States obtain drinking water from private wells (8). Based on recent studies, the EPA MCL for nitrates was exceeded by 13.4% of household wells in nine states in the Midwest (9) and 9% of household wells nationally (10). Because of the risks for potential adverse health effects, persons who use drinking water that contains nitrate levels >10 mg/L or other contaminants exceeding the EPA MCL should have alternative sources of water or appropriate treatment of existing supplies. Information regarding testing of well water may be obtained from city or county health departments.

Spontaneous abortions occur commonly, are directly associated with increasing maternal age, and may cluster by chance. Possible explanations for the cases of spontaneous abortion investigated by LCHD are that they may represent an otherwise unrelated cluster or that they may have been related to ingestion of nitrate-contaminated drinking water. Term births occurred before or after the period when each of the four women consumed contaminated water, and spontaneous abortions occurred coincident with the period of nitrate exposure. However, spontaneous abortions frequently are preceded or followed by live births, and this investigation did not compare the rate of spontaneous abortions in other residents of the community who either were or were not exposed to nitrate-contaminated water. Although this investigation did not establish a causal link between spontaneous abortion and nitrate exposure, the findings indicate the need for further assessment of the possible effects of this common groundwater contaminant on human reproduction.

Since 1971, EPA and CDC have maintained a surveillance system to monitor the occurrence of waterborne disease outbreaks. Illnesses related to exposures to pathogens and chemicals associated with recreational water use or ingestion of drinking water should be reported to the Epidemiology Branch, Division of Parasitic Diseases, National Center for Infectious Diseases, CDC, telephone (770) 488-7760.

References

1. Kross BC, Ayebo AD, Fuortes LJ. Methemoglobinemia: nitrate toxicity in rural America. Am Fam Phys 1992;46:183-8.

2. Food and Drug Administration. Teratologic evaluation of FDA 71-7 (sodium nitrate). Washington, DC: US Department of Health and Human Services, Public Health Service, Food and Drug Administration, 1972; publication no. PB 221775.

3. Sund J, Wright MJ, Simon J. Weeds containing nitrate cause abortion in cattle. Agronomy Journal 1957;49:278-9.

4. Muhrer ME, Garner GB, Pfander WH, et al. The effect of nitrate on reproduction and lactation. J An Sci 1959;15:1291-2.

5. Dorsch MM, Scragg RKR, McMichael AJ, et al. Congenital malformations and maternal drinking water supply in rural South Australia: a case-control study. J Epidemiol 1984;119:473-86.

6. Arbuckle TE, Sherman GJ, Corey PN, et al. Water nitrates and CNS birth defects: a population-based case-controlled study. Arch Environ Health 1988;43:162-7.

7. Schmitz JT. Methemoglobinemia: cause of abortions? Obstet Gynecol 1961;17:413-5.

8. Bureau of the Census. The Housing Survey of the United States, 1993. Washington, DC: US Department of Commerce, Economics and Statistics Administration, Bureau of the Census, 1993

9. CDC. Interim report: a survey of the presence of contaminants in water from private wells in nine Midwestern states. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, CDC, April 1996.

10. US Geological Survey. Nutrients in ground water and surface water of the United States: an analysis of data through 1992. Reston, Virginia: US Geological Survey, 1995.

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