Nitrates in drinking water and methemoglobin levels in pregnancy: a longitudinal study.

BACKGROUND: Private water systems are more likely to have nitrate levels above the maximum contaminant level (MCL). Pregnant women are considered vulnerable to the effects of exposure to high levels of nitrates in drinking water due to their altered physiological states. The level of methemoglobin in the blood is the biomarker often used in research for assessing exposure to nitrates. The objective of this study was to assess methemoglobin levels and examine how various factors affected methemoglobin levels during pregnancy. We also examined whether differences in water use practices existed among pregnant women based on household drinking water source of private vs. public supply. METHODS: A longitudinal study of 357 pregnant women was conducted. Longitudinal regression models were used to examine changes and predictors of the change in methemoglobin levels over the period of gestation. RESULTS: Pregnant women showed a decrease in methemoglobin levels with increasing gestation although <1% had levels above the physiologic normal of 2% methemoglobin, regardless of the source of their drinking water. The multivariable analyses did not show a statistically significant association between methemoglobin levels and the estimated nitrate intake from tap water among pregnant women around 36 weeks gestation (ß = 0.046, p = 0.986). Four women had tap water nitrate levels above the MCL of 10 mg/L. At enrollment, a greater proportion of women who reported using water treatment devices were private wells users (66%) compared to public system users (46%) (p < 0.0001). Also, a greater proportion of private well users (27%) compared to public system users (13%) were using devices capable of removing nitrate from water (p < 0.0001). CONCLUSION: Pregnant women potentially exposed to nitrate levels primarily below the MCL for drinking water were unlikely to show methemoglobin levels above the physiologic normal. Water use practices such as the use of treatment devices to remove nitrates varied according to water source and should be considered in the assessment of exposure to nitrates in future studies.

Job strain and risk of musculoskeletal symptoms among a prospective cohort of occupational computer users.

OBJECTIVES: Most previous studies of the association between psychosocial stress and musculoskeletal illness among computer users have been cross-sectional and have yielded inconsistent results. The association between a measure of psychosocial stress, "job strain", and incident neck-shoulder and arm-hand musculoskeletal symptoms was investigated among recently hired computer users. METHODS: The participants worked for one of several large employers and were followed prospectively for 6 months. The "job demands" and "decision latitude" subscales of the Job Content Questionnaire were used to estimate the job-strain quadrants and a ratio measure of job strain which was subsequently categorized. Incident musculoskeletal symptoms were obtained with weekly diaries. Proportional hazards models were used to estimate associations between job strain and incident musculoskeletal symptoms. RESULTS: Those in the high-strain quadrant were at increased risk of neck-shoulder symptoms [hazard ratio (HR) 1.65, 95% confidence interval (95% CI) 0.91-2.99] when compared with those in the low-strain quadrant. Those in the highest strain-ratio category were also at increased risk of neck-shoulder symptoms when compared with those in the lowest strain-ratio category (HR 1.52, 95% CI 0.88-2.62). Modification by previous years of computer use was observed, with an elevated risk observed for those in the highest job-strain ratio category who also had low previous computer use (HR 3.16, 95% CI 1.25-8.00). There did not appear to be an association between either measure of job strain and incident arm-hand symptoms. CONCLUSIONS: In this cohort, workers who reported high job strain were more likely to develop neck-shoulder symptoms.

Fentanyl-associated fatalities among illicit drug users in Wayne County, Michigan (July 2005-May 2006).

BACKGROUND: During the summer of 2005, multiple cities in the United States began to report outbreaks of fentanyl-associated fatalities among illicit drug users. The objectives of this study were to (1) determine if an outbreak of fentanyl-associated fatalities occurred in mid-2005 to mid-2006 and (2) to examine trends and compare features of fentanyl-contaminated heroin-associated fatalities (FHFs) with non-fentanyl, heroin-associated fatalities (NFHFs) among illicit drug users. METHODS: Baseline prevalence of fentanyl- and heroin-associated deaths was estimated from January to May 2005 based on recorded cause of death (determined by the medical examiner (ME)) using the Wayne County, MI, USA toxicology database. The database was then queried for both FHFs and NFHFs between July 1, 2005 and May 12, 2006. A FHF was defined as having fentanyl or norfentanyl (metabolite) detected in any postmortem biological sample and either (1) detection of heroin or its metabolite (6-acetylmorphine) and/or cocaine or its metabolite (benzoylecgonine) in a postmortem biological specimen or (2) confirmation of fentanyl abuse as the cause of death by the ME or a medical history available sufficient enough to exclude prescription fentanyl or other therapeutic opioid use. A NFHF was defined as detection of heroin, 6-acetylmorphine (heroin metabolite) or morphine in any postmortem biological specimen, heroin overdose listed as the cause of death by the ME, and absence of fentanyl detection on postmortem laboratory testing. Information was systematically collected, trended for each group and then compared between the two groups with regard to demographic, exposure, autopsy, and toxicology data. Logistic regression was performed using SAS v 9.1 examining the effects of age, gender, and marital status with fentanyl group status. RESULTS: Monthly prevalence of fentanyl-associated fatalities among illicit drug users increased from an average of two in early 2005 to a peak of 24 in May, 2006. In total, 101 FHFs and 90 NFHFs were analyzed. The median age of decedents was 46 and 45 years for the fentanyl and non-fentanyl groups, respectively. Fentanyl-contaminated heroin-associated fatalities (FHFs) were more likely to be female (p = 0.003). Women aged over 44 years (OR = 4.67;95 % CI = 1.29-16.96) and divorced/widowed women (OR = 14.18;95 % CI = 1.59-127.01) were more likely to be FHFs when compared to women aged less than 44 years and single, respectively. A significant interaction occurred between gender and age, and gender and marital status. Most FHFs had central (heart) blood samples available for fentanyl testing (n = 96; 95 %): fentanyl was detected in most (n = 91; 95 %). Of these, close to half had no detectable heroin (or 6-acetylmorphine) concentrations (n = 37; 40.7 %). About half of these samples had detectable cocaine concentrations (n = 20; 54 %). Median fentanyl concentration in central blood samples was 0.02 µg/ml (n = 91, range <0.002-0.051 µg/ml) and 0.02 µg/ml (n = 32, range <0.004-0.069 µg/ml) in peripheral blood samples. The geometric mean of the ratio of central to peripheral values was 2.10 (median C/P = 1.75). At autopsy, pulmonary edema was the most frequently encountered finding for both groups (77 %). CONCLUSION: Illicit drugs may contain undeclared ingredients that may increase the likelihood of fatality in users. Gender differences in fentanyl-related mortality may be modified by age and/or marital status. These findings may help inform public health and prevention activities if fatalities associated with fentanyl-contaminated illicit drugs reoccur.

In utero exposure to a brominated flame retardant and male growth and development.

Whether environmental exposures alter the timing of puberty is the subject of increasing interest as pubertal age may have consequences for long term health. This study examines the association between exposure to a brominated flame retardant, polybrominated biphenyl (PBB), and puberty and growth. The population consists of sons born to women accidentally exposed to PBBs during 1973-74. Sons 5 to 17 years reported Tanner Stages and answered questions regarding current growth in a mailed questionnaire. Sons 18 to 30 years of age participated in a telephone interview in which they reported retrospective measures of development. Among sons 5-17 years, those with highest exposure (>3 ppb) were less likely to report advanced Tanner stage genital development (OR=0.4, 95% CI: 0.2-0.9) and were less likely to report advanced pubic hair development (OR=0.5; 95% CI: 0.2-1.0), after adjusting for current age, compared to those with lowest exposure (<= 1 ppb). No differences were seen in growth among sons 5-17. However, among sons 18-30 years, those with higher exposure were more likely to weigh less and have lower BMI as adults (test of trend p=0.01 and 0.04, respectively). They were less likely to recall being tall (OR=0.5; 95% CI 0.2-0.9) or heavy (OR=0.6; 95% CI 0.3-1.1) compared to their peers at age 11 years. These results suggest that sons exposed to PBBs in utero may be more likely to have delayed puberty. Further research is needed to corroborate these findings among structurally related compounds and shed light on the biological mechanisms that may be disrupted during puberty and development.

Keyboard use and musculoskeletal outcomes among computer users.

BACKGROUND: In this review, the epidemiological evidence examining associations between upper extremity musculoskeletal symptoms and disorders and keyboard use intensity (hours of computer use-per day or per-week) and computer user posture was explored. METHODS: An OVID Medline literature search was conducted to identify papers published in the peer-reviewed medical literature between 1966 and November, 2005. A total of 558 citations were found and reviewed. Those papers in which associations between musculoskeletal outcomes and (1) posture (ascertained by a study investigator) or (2) computer use, in units of hours-per-day, hours-per-week, or as a percent of work-time, were included in the review. RESULTS: Thirty-nine epidemiological studies examining associations between computer use and MSD outcomes were identified. While the observational epidemiological literature was heterogeneous, some trends did emerge. It appears that the most consistent finding was the association observed between hours keying and hand/arm outcomes. Associations between some postural effects and musculoskeletal outcomes may also be inferred from the literature. In particular, placing the keyboard below the elbow, limiting head rotation, and resting the arms appears to result in reduced risk of neck/shoulder outcomes. Minimizing ulnar deviation and keyboard thickness appears to result in reduced risk of hand/arm outcomes. CONCLUSIONS: Several methodological limitations, including non-representative samples, imprecise or biased measures of exposure and health outcome, incomplete control of confounding, and reversal of cause and effect, may contribute to the heterogeneity of observed results. Suggestions are made for improving the validity of future investigations.