Trihalomethane exposures from municipal water supplies and selected congenital malformations.

BACKGROUND: Concerns about potential health effects of trihalomethanes (THMs) have prompted investigations on whether infants whose mothers were periconceptionally exposed to drinking water containing THMs are at greater risk of congenital malformations. METHODS: We used two large case-control maternal interview studies that were conducted among California deliveries from 1987 through 1991. One study comprised 538 infants/fetuses with neural tube defects (NTDs) and 539 nonmalformed control infants. The second study included an additional 265 infants with NTDs, 207 infants with conotruncal heart defects, 409 infants with orofacial clefts, and 481 control infants. Expert personnel from municipal water companies estimated THM levels for a particular residence and specific periconceptional time period using quarterly monitoring measurements. Estimates were also made for four individual THM levels and for the total THM level. RESULTS: NTD risk in the first study was inversely associated with total THM exposure. Although the second study did not show the same inverse relationship for NTDs, there were no positive associations of NTDs or the other malformations with total THM as estimated from continuous models. Elevated risks were observed for the lowest category of exposure (1-24 ppb), but risks were either not substantially elevated or were imprecise for higher exposure levels. Thus no evidence was observed for an exposure-response relation. CONCLUSIONS: Our results do not provide a clear pattern of association between THM exposure and risks of specific congenital malformations. Imprecise exposure measures coupled with a lack of information about other possible sources of THM exposure may have caused associations to be underestimated.

A nested case-control study of residential and personal magnetic field measures and miscarriages.

We conducted a nested case-control study (177 cases, 550 controls) to assess the relation between retrospective magnetic field measures and clinical miscarriage among members of the northern California Kaiser Permanente medical care system. We also conducted a prospective substudy of 219 participants of the same parent cohort to determine whether 12-week and 30-week exposure assessments were similar. We evaluated wire codes, area measures, and three personal meter metrics: (1) the average difference between consecutive levels (a rate-of-change metric), (2) the maximum level, and (3) the time-weighted average. For wire codes and area measures we found little association. For the personal metrics (30 weeks after last menstrual period), we found positive associations. Each exposure was divided into quartiles, with the lowest quartile as referent. Starting with the highest quartile, adjusted odds ratios and 95% confidence intervals were 3.1 (95% CI = 1.6-6.0), 2.3 (95% CI = 1.2-4.4), and 1.5 (95% CI = 0.8-3.1) for the rate-of-change metric; 2.3 (95% CI = 1.2-4.4), 1.9 (95% CI = 1.0-3.5), and 1.4 (95% CI = 0.7-2.8) for the maximum value; and 1.7 (95% CI = 0.9-3.3), 1.7 (95% CI = 0.9-3.3), and 1.7 (95% CI = 0.9-3.3) for the time-weighted average. The odds ratio conveyed by being above a 24-hour time-weighted average of 2 milligauss was 1.0 (95% CI = 0.5-2.1). Exposure assessment measurements at 12 weeks were poorly correlated with those taken at 30 weeks. Nonetheless, the prospective substudy results regarding miscarriage risk were consistent with the nested study results.

Childhood asthma along the United States/Mexico border: hospitalizations and air quality in two California counties

Since the passage of the North American Free Trade Agreement in 1993, there has been an increasing need to monitor environmental health trends that may be related to the rapid industrialization of the United States/Mexico border. We studied two counties on the California/Baja California border to obtain baseline data on trends in childhood asthma hospitalizations and two pollutants that aggravate asthma, ozone and particulate matter (less than 10 microns in diameter), from 1983 to 1994. Hospital discharge records of children 14 years and younger were analyzed, and rates by county, race, and sex were age-adjusted to the 1990 California population. Data on five ozone and particulate matter indices obtained from the California Environmental Protection Agency were used. Imperial County had the highest childhood asthma hospitalization rates in California for non-Hispanic whites and African-Americans, and the second highest for Hispanics. San Diego County had rates below the state average. Over the County decreased 9 por ciento. Maximum ozone levels increased 64 por ciento in Imperial County but decreased 46 por ciento in San Diego County. High rates of childhood asthma hospitalizations in Imperial County may be partially related to high levels of poverty and worsening air quality conditions produced by increased burdens on the local airshed. Asthma prevalence surveys and binational time-series analyses examining asthma-pollutant relationships are needed

Childhood asthma along the United States/Mexico border: hospitalizations and air quality in two California counties

Since the passage of the North American Free Trade Agreement in 1993, there has been an increasing need to monitor environmental health trends that may be related to the rapid industrialization of the United States/Mexico border. We studied two counties on the California/Baja California border to obtain baseline data on trends in childhood asthma hospitalizations and two pollutants that aggravate asthma, ozone and particulate matter (less than 10 microns in diameter), from 1983 to 1994. Hospital discharge records of children 14 years and younger were analyzed, and rates by county, race, and sex were age-adjusted to the 1990 California population. Data on five ozone and particulate matter indices obtained from the California Environmental Protection Agency were used. Imperial County had the highest childhood asthma hospitalization rates in California for non-Hispanic whites and African-Americans, and the second highest for Hispanics. San Diego County had rates below the state average. Over the County decreased 9 por ciento. Maximum ozone levels increased 64 por ciento in Imperial County but decreased 46 por ciento in San Diego County. High rates of childhood asthma hospitalizations in Imperial County may be partially related to high levels of poverty and worsening air quality conditions produced by increased burdens on the local airshed. Asthma prevalence surveys and binational time-series analyses examining asthma-pollutant relationships are needed