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: 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

Spontaneous Abortions - Continued

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 populationbased 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

Spontaneous Abortions - Continued

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.

Notice to Readers

Publication of Updated Guide for Developing Policies

For HIV-Infected Students and School Staff

The National Association of State Boards of Education (NASBE) is one of 30 national organizations that receive assistance from CDC to help schools provide effective health education to prevent the spread of human immunodeficiency virus (HIV). As part of its education mission, NASBE has published the second edition of its guide Someone at School Has AIDS: A Complete Guide to Education Policies Concerning HIV Infection (1).

To develop the guide, NASBE convened experts in medicine, public health, education, and law* who recommended scientifically and legally based policy statements that local and state departments of education can use in developing policies for students and staff who are infected with HIV. The guide addresses infection control, confidentiality, and HIV-antibody testing. The second edition includes sections on HIV prevention, counseling and testing, support services, HIV and athletics, and community relations and provides a legal context for policy recommendations within the parameters established by the Americans with Disabilities Act, the Individuals with Disabilities Education Act, the Occupational Safety and Health Administration's infection-control guidelines, and the Family Educational Rights and Privacy Act.

Copies of the guide are available from NASBE, 1012 Cameron Street, Alexandria, VA 22314; telephone (800) 220-5183 or (703) 684-4000.

Reference

1. National Association of State Boards of Education. Someone at school has AIDS: a complete guide to education policies concerning HIV infection. 2nd ed. Alexandria, Virginia: National Association of State Boards of Education, 1996.

* Representatives of the following organizations participated in developing and/or reviewing the guide: Advocates for Youth, Alabama Department of Education, American Academy of Pediatrics, American Medical Association, American Red Cross, Association of State and Territorial Health Officials, California State Board of Education, CDC, Council for Exceptional Children, Council of Chief State School Officers, Council of Great City Schools, Idaho Department of Health and Welfare, Indian Health Service, Kansas Board of Education, Maryland Department of Education, Massachusetts State Department of Education, National Alliance of State and Territorial AIDS Directors, National Association for Sport and Physical Education, National Association of People with AIDS, National Association of School Nurses, National Association of Secondary School Principals, National Association of State Directors of Special Education, National Catholic Educational Association, National Coalition of Advocates for Students, National Education Association, National Federation of State High School Associations, National Middle School Association, National PTA, National School Boards Association, National School Health Association, Nebraska Department of Education, Northside (San Antonio) Health Careers High School, Ryan White Foundation, South Carolina Department of Education, U.S. Department of Education, U.S. Department of Justice, Utah State Office of Education, Virginia Department of Education, Washington Department of Public Instruction, and West Virginia Department of Education.

FIGURE I. Selected notifiable disease reports, comparison of 4-week totals ending June 29, 1996, with historical data United States

*Ratio of current 4-week total to mean of 15 4-week totals (from previous, comparable, and subsequent 4-week periods for the past 5 years). The point where the hatched area begins is based on the mean and two standard deviations of these 4-week totals.

cases of selected notifiable diseases, United States, cumulative, week ending June 29, 1996 (26th Week)

TABLE I. Summary

*Not notifiable in all states.

Updated weekly from reports to the Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases (NCID). Updated monthly to the Division of HIV/AIDS Prevention, National Center for HIV, STD, and TB Prevention (NCHSTP), last update June 25, 1996.

1 One suspected case of polio with onset in 1996 has been reported to date.

**Updated quarterly from reports to the Division of STD Prevention, NCHSTP. First quarter 1996 is not yet available.

TABLE II. Cases of selected notifiable diseases, United States, weeks ending June 29, 1996, and July 1, 1995 (26th Week)

*Updated monthly to the Division of HIV/AIDS Prevention, National Center for HIV, STD, and TB Prevention, last update June 25, 1996. *National Electronic Telecommunications System for Surveillance.

$ Public Health Laboratory Information System.