Concern with health effects of extremely low frequency magnetic fields has been raised by epidemiologic studies of childhood cancer in relation to proximity to electric power distribution lines. This case-control study was designed to assess the relation between residential exposure to magnetic fields and the development of childhood cancer. Eligible cases consisted of all 356 residents of the five-county 1970 Denver, Colorado Standard Metropolitan Statistical Area aged 0-14 years who were diagnosed with any form of cancer between 1976 and 1983. Controls were selected by random digit dialing to approximate the case distribution by age, sex, and telephone exchange area. Exposure was characterized through in-home electric and magnetic field measurements under low and high power use conditions and wire configuration codes, a surrogate measure of long-term magnetic field levels. Measured magnetic fields under low power use conditions had a modest association with cancer incidence; a cutoff score of 2.0 milligauss resulted in an odds ratio of 1.4 (95% confidence interval (CI) = 0.6-2.9) for total cancers and somewhat larger odds ratios (ORs) for leukemias (OR = 1.9), lymphomas (OR = 2.2), and soft tissue sarcomas (OR = 3.3). Neither magnetic fields (OR = 1.0) nor electric fields (OR = 0.9) under high power use conditions were related to total cancers. Wire codes associated with higher magnetic fields were more common among case than control homes. The odds ratio to contrast very high and high to very low, low, and buried wire codes was 1.5 (95% CI = 1.0-2.3) for total cases, with consistency across cancer subgroups except for brain cancer (OR = 2.0) and lymphomas (OR = 0.8). Contrasts of very high to buried wire code homes produced larger, less precise odds ratios of 2.3 for total cases, 2.9 for leukemias, and 3.3 for lymphomas. Adjusted estimates for measured fields and wire codes did not differ from crude results, indicating an absence of confounding. Limitations to the study are nonresponse (especially for field measurements), differential mobility of cases and controls, and a presumably nondifferential exposure misclassification from the use of imperfect surrogates for long-term magnetic field exposure history. In spite of these concerns, the results encourage further examination of the carcinogenic potential from this form of nonionizing radiation.

Objective and sourcesWe reviewed the epidemiologic literature for PFOA.Data synthesisPerfluorooctanoic acid (PFOA) does not occur naturally but is present in the serum of most residents of industrialized countries (U.S. median, 4 ng/mL). Drinking water is the primary route of exposure in some populations, but exposure sources are not well understood. PFOA has been used to manufacture such products as Gore-Tex and Teflon. PFOA does not break down in the environment; the human half-life is estimated at about 3 years. PFOA is not metabolized in the body; it is not lipophilic. PFOA is not directly genotoxic; animal data indicate that it can cause several types of tumors and neonatal death and may have toxic effects on the immune, liver, and endocrine systems. Data on the human health effects of PFOA are sparse. There is relatively consistent evidence of modest positive associations with cholesterol and uric acid, although the magnitude of the cholesterol effect is inconsistent across different exposure levels. There is some but much less consistent evidence of a modest positive correlation with liver enzymes. Most findings come from cross-sectional studies, limiting conclusions. Two occupational cohort studies do not provide consistent evidence for chronic disease; both are limited by sample size and reliance on mortality data. Reproductive data have increased recently but are inconsistent, and any observed adverse effects are modest.ConclusionsEpidemiologic evidence remains limited, and to date data are insufficient to draw firm conclusions regarding the role of PFOA for any of the diseases of concern.

Although there are biological pathways that conceivably might link stress with preterm birth, studies attempting to demonstrate such a relationship have given conflicting results. For the most part, social support has not been found to reduce preterm births. The present study is a prospective examination of how such factors as life events, social support, depression, and anxiety related to pregnancy may be associated with birth before 37 weeks' gestation. The study cohort included 1962 women who gave birth in central North Carolina in the years 1996-2000. Participants, aged 16 years and older, were entered into the study at 24-29 weeks' gestation. Many subjects were African-American women, and about half were nulliparous. More than half were not married when entering the study. Low-income households were liberally represented in the study group. The incidence of preterm birth was 12%.Life events, social support, and depression were not associated with preterm birth in this study, but women having medium and high scores for self-rated pregnancy-related anxiety were at increased risk; risk ratios were 1.5 and 2.1, respectively. High scores on a scale of perceived racial discrimination also correlated with an increased risk of preterm birth (risk ratio, 1.4). Similar findings were obtained when alcohol or tobacco use was taken into account. Women with greater self-rated anxiety were more at risk of spontaneous than of medically indicated preterm birth. A risk ratio of 1.8 was associated with life events perceived as having had a negative impact. Among women with negative life events, pregnancy-related anxiety was associated with preterm birth triggered by either labor or ruptured membranes. The association between high levels of pregnancy-related anxiety and preterm birth was less marked when limited to women lacking comorbid medical conditions, but it persisted.These findings suggest that some psychosocial measures are in fact associated with preterm birth.

Few population-based data exist that describe leisure-time physical activity among pregnant women. The purpose of this study was to characterise the prevalence of leisure activity and to examine characteristics associated with participation in leisure activity during pregnancy. Using data collected from the year 2000 Behavioral Risk Factor Surveillance System, information on leisure activity was collected during telephone interviews from 1979 pregnant women and 44,657 non-pregnant women 18-44 years of age, representative of the US population. The prevalence of any leisure activity in the past month was 65.6%, 95% confidence interval [95% CI] 62.0, 69.1, among pregnant women and 73.1% [95% CI 72.4, 73.9] among non-pregnant women. The prevalence of recommended activity was also lower among pregnant women than non-pregnant women (15.8% vs. 26.1%). The most common leisure activity for pregnant women was walking, followed by activities such as swimming laps, weight lifting, gardening, and aerobics. Among pregnant women, any leisure activity was significantly higher for those with higher education, younger age, and excellent or very good health than for those with fair or poor health. Pregnant women reported less leisure activity than non-pregnant women of the same age. Studies to understand the enablers and barriers to participating in leisure activity during pregnancy are needed.

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