Long-term nitrogen dioxide exposure and cause-specific mortality in the U.S. Medicare population

BACKGROUND

Since 1971, the annual National Ambient Air Quality Standard (NAAQS) for nitrogen dioxide (NO₂) has remained at 53 ppb, the impact of long-term NO₂ exposure on mortality is poorly understood.

OBJECTIVES

We examined associations between long-term NO₂ exposure (12-month moving average of NO₂) below the annual NAAQS and cause-specific mortality among the older adults in the U.S.

METHODS

Cox proportional-hazard models were used to estimate Hazard Ratio (HR) for cause-specific mortality associated with long-term NO₂ exposures among about 50 million Medicare beneficiaries living within the conterminous U.S. from 2001 to 2008.

RESULTS

A 10 ppb increase in NO₂ was associated with increased mortality from all-cause (HR: 1.06; 95% CI: 1.05-1.06), cardiovascular (HR: 1.10; 95% CI: 1.10-1.11), respiratory disease (HR: 1.09; 95% CI: 1.08-1.11), and cancer (HR: 1.01; 95% CI: 1.00-1.02) adjusting for age, sex, race, ZIP code as strata ZIP code- and state-level socio-economic status (SES) as covariates, and PM_2.5 exposure using a 2-stage approach. NO₂ was also associated with elevated mortality from ischemic heart disease, cerebrovascular disease, congestive heart failure, chronic obstructive pulmonary disease, pneumonia, and lung cancer. We found no evidence of a threshold, with positive and significant HRs across the range of NO₂ exposures for all causes of death examined. Exposure-response curves were linear for all-cause, supra-linear for cardiovascular-, and sub-linear for respiratory-related mortality. HRs were highest consistently among Black beneficiaries.

CONCLUSIONS

Long-term NO₂ exposure is associated with elevated risks of death by multiple causes, without evidence of a threshold response. Our findings raise concerns about the sufficiency of the annual NAAQS for NO₂.

Household use of crop residues and fuelwood for cooking and newborn birth size in rural Bangladesh

OBJECTIVES

We aimed to investigate the association between type of cooking biomass fuels (crop residues vs fuelwood) and newborn birth outcomes in Bangladeshi children.

METHODS

In this birth cohort study, pregnant women who were 18 years or older with ultrasound confirmed singleton pregnancy of ≤16 weeks of gestation were enrolled from two Bangladesh clinics between January 2008 and June 2011. Exposure to cooking biomass fuels during pregnancy was assessed by an administered questionnaire. The newborn size metrics were measured at the time of delivery. We used multiple linear regression and logistic regression to assess the associations between the type of cooking biomass fuels and birth outcomes after adjusting for covariates.

RESULTS

A total of 1137 participants were using biomass fuels, including crop residues (30.3%) and fuelwood (69.7%), respectively, for cooking. After adjusting for covariates, the use of crop residues for cooking was associated with a 0.13 SD decrease in birth length (95% CI 0.25 to -0.01), a 0.14 SD decrease in head circumference (95% CI -0.27 to -0.02), and increased risk of low birth weight (LBW, OR 1.52, 95% CI 1.07 to 2.15) compared with the use of fuelwood.

CONCLUSION

The use of crop residues for cooking was associated with reduced birth size and increased risk for LBW in Bangladeshi children, implying that the use of crop residues during pregnancy may have a detrimental effect on fetal growth.

The impact of Long-Term PM2.5 constituents and their sources on specific causes of death in a US Medicare cohort

BACKGROUND

Our understanding of the impact of long-term exposures to PM_2.5 constituents and sources on mortality is limited.

OBJECTIVES

To examine associations between long-term exposures to PM_2.5 constituents and sources and cause-specific mortality in US older adults.

METHODS

We obtained demographic and mortality data for 15.4 million Medicare beneficiaries living within the conterminous United States (US) between 2000 and 2008. We assessed PM_2.5 constituents exposures for each beneficiary and used factor analysis and residual-based methods to characterize PM_2.5 sources and mixtures, respectively. In age-, sex-, race- and site- stratified Cox proportional hazard models adjusted for neighborhood socio-economic status (SES), we assessed associations of individual PM_2.5 constituents, sources, and mixtures and cause-specific mortality and examined modification of these associations by participant demographics and location of residence. We assessed the robustness of our findings to additional adjustment for behavioral risk factors and to alternate exposure definitions and exposure windows.

RESULTS

Hazard ratios (HR) were highest for all causes of death, except COPD, for PM_2.5 constituents and the coal combustion-related PM_2.5 components, with no evidence of confounding by behavioral covariates. We further found Pb and metal-related PM_2.5 components to be significantly associated with increased HR of all causes of death, except COPD and lung cancer mortality, and nitrate (NO₃^-) and silicon (Si) and associated source-related PM_2.5 components (traffic and soil, respectively) to be significantly associated with increased all-cause, CVD, respiratory and all cancer-related mortality HR. Associations for other examined constituents and mortality were inconsistent or largely null. Our analyses of mixtures were generally consistent with these findings. Mortality HRs were greatest for minority, especially Black, low-income urban, younger, and male beneficiaries.

DISCUSSION

PM_2.5 components related to coal combustion, traffic, and to a lesser extent, soil were strongly associated with mortality from CVD, respiratory disease, and cancer.

Non-nutritive suck and airborne metal exposures among Puerto Rican infants

Air pollution has been shown to impact multiple measures of neurodevelopment in young children. Its effects on particularly vulnerable populations, such as ethnic minorities, however, is less studied. To address this gap in the literature, we assess the associations between infant non-nutritive suck (NNS), an early indicator of central nervous system integrity, and air pollution exposures in Puerto Rico. Among infants aged 0-3 months enrolled in the Center for Research on Early Childhood Exposure and Development (CRECE) cohort from 2017 to 2019, we examined associations between exposure to fine particulate matter (PM_2.5) and its components on infant NNS in Puerto Rico. NNS was assessed using a pacifier attached to a pressure transducer, allowing for real-time visualization of NNS amplitude, frequency, duration, cycles/burst, cycles/min and bursts/min. These data were linked to 9-month average prenatal concentrations of PM_2.5 and components, measured at three community monitoring sites. We used linear regression to examine the PM_2.5-NNS association in single pollutant models, controlling for infant sex, maternal age, gestational age, and season of birth in base and additionally for household smoke exposure, age at testing, and NNS duration in full models. Among 198 infants, the average NNS amplitude and burst duration was 17.1 cmH₂O and 6.1 s, respectively. Decreased NNS amplitude was consistently and significantly associated with 9-month average exposure to sulfur (-1.026 ± 0.507), zinc (-1.091 ± 0.503), copper (-1.096 ± 0.535) vanadium (-1.157 ± 0.537), and nickel (-1.530 ± 0.501). Decrements in NNS frequency were associated with sulfur exposure (0.036 ± 0.018), but not other examined PM components. Our findings provide new evidence that prenatal maternal exposure to specific PM components are associated with impaired neurodevelopment in Puerto Rican infants soon after birth.

Umbilical Cord Blood Metal Mixtures and Birth Size in Bangladeshi Children

BACKGROUND

Studies have evaluated environmental exposure to toxic metals such as arsenic (As), cadmium (Cd), manganese (Mn), or lead (Pb) on birth size; however, information on potential effects of exposures to metal mixtures is limited.

OBJECTIVES

We assessed the association between metal mixtures (As, Cd, Mn, Pb) in umbilical cord blood and neonate size in Bangladeshi children.

METHODS

In this birth cohort study, pregnant women who were ≥18 years of age with an ultrasound-confirmed singleton pregnancy of ≤16wk gestation were recruited from two Bangladesh clinics between 2008 and 2011. Neonate size metrics were measured at the time of delivery. Metals in cord blood were measured using inductively coupled plasma mass spectrometry. We employed multivariable linear regression and Bayesian kernel machine regression (BKMR) to estimate associations of individual metals and metal mixtures with birth size parameters.

RESULTS

Data from 1,088 participants was assessed. We found a significant negative association between metal mixture and birth length and head circumference when all metal concentrations were above the 60th and 55th percentiles, respectively, compared with the median. An interquartile range (IQR) increase in log Cd concentration {log[Cd (in micrograms per deciliter)] IQR=2.51} was associated with a 0.13-standard deviation (SD) decrease in mean birth length (95% CI: -0.25, -0.02) and a 0.17-SD decrease in mean head circumference (95% CI: -0.28, -0.05), based on linear regression models adjusted for covariates and the other metals. An IQR increase in log Mn concentration {log[Mn (in micrograms per deciliter)] IQR=0.69} was associated with a 0.07-SD decrease in mean birth weight (95% CI: -0.15, 0.002).

DISCUSSION

Metal mixtures in cord blood were associated with reduced birth size in Bangladeshi children. Results from linear regression models adjusted and the BKMR mixtures analyses suggest adverse effects of Cd and Mn, as individual metal exposures, on birth size outcomes. https://doi.org/10.1289/EHP7502.

Long-term ozone exposures and cause-specific mortality in a US Medicare cohort

We examined the association of long-term, daily 1-h maximum O₃ (ozone) exposures on cause-specific mortality for 22.2 million US Medicare beneficiaries between 2000-2008. We modeled the association between O₃ and mortality using age-gender-race stratified log-linear regression models, adjusted for state of residence. We examined confounding by (1) adjusting for PM_2.5 (particles with aerodynamic diameters <2.5 μm) and NO₂ (nitrogen dioxide) exposures, temperature, and neighborhood-level characteristics and behaviors, and (2) decomposing O₃ into its temporal and spatio-temporal components and comparing estimated risk ratios. We also examined sensitivity of our results to alternate exposure measures based on warm-season 8-h daily maximum and 24-h average exposures. We found increased risks from long-term O₃ exposures to be strongest and most consistent for mortality from respiratory disease (1.030, 95% CI: 1.027, 1.034) (including COPD (chronic obstructive pulmonary disease)), CHF (congestive heart failure), and lung cancer (1.015, 95% CI: 1.010, 1.020), with no evidence of confounding by PM_2.5, NO₂, and temperature and with results similar across O₃ exposure measures. While significant, associations between long-term O₃ exposures and CVD (cardiovascular)-related mortality (1.005, 95% CI: 1.003, 1.007) were confounded by PM_2.5 and varied with the exposure measure, with associations no longer significantly positive when warm-season 8-h maximum or 24-h average O₃ was used to assess exposures. In this large study, we provide strong evidence that O₃ exposure is associated with mortality from respiratory-related causes and for the first-time, lung cancer, but raise questions regarding O₃-related impacts on CVD mortality. Our findings demonstrate the need to further identify potential confounders.

The impact of long-term PM2.5 exposure on specific causes of death: exposure-response curves and effect modification among 53 million U.S. Medicare beneficiaries

BACKGROUND

The shape of the exposure-response curve for long-term ambient fine particulate (PM_2.5) exposure and cause-specific mortality is poorly understood, especially for rural populations and underrepresented minorities.

METHODS

We used hybrid machine learning and Cox proportional hazard models to assess the association of long-term PM_2.5 exposures on specific causes of death for 53 million U.S. Medicare beneficiaries (aged ≥65) from 2000 to 2008. Models included strata for age, sex, race, and ZIP code and controlled for neighborhood socio-economic status (SES) in our main analyses, with approximately 4 billion person-months of follow-up, and additionally for warm season average of 1-h daily maximum ozone exposures in a sensitivity analysis. The impact of non-traffic PM_2.5 on mortality was examined using two stage models of PM_2.5 and nitrogen dioxide (NO₂).

RESULTS

A 10 μg /m³ increase in 12-month average PM_2.5 prior to death was associated with a 5% increase in all-cause mortality, as well as an 8.8, 5.6, and 2.5% increase in all cardiovascular disease (CVD)-, all respiratory-, and all cancer deaths, respectively, in age, gender, race, ZIP code, and SES-adjusted models. PM_2.5 exposures, however, were not associated with lung cancer mortality. Results were not sensitive to control for ozone exposures. PM_2.5-mortality associations for CVD- and respiratory-related causes were positive and significant for beneficiaries irrespective of their sex, race, age, SES and urbanicity, with no evidence of a lower threshold for response or of lower Risk Ratios (RRs) at low PM_2.5 levels. Associations between PM_2.5 and CVD and respiratory mortality were linear and were higher for younger, Black and urban beneficiaries, but were largely similar by SES. Risks associated with non-traffic PM_2.5 were lower than that for all PM_2.5 and were null for respiratory and lung cancer-related deaths.

CONCLUSIONS

PM_2.5 was associated with mortality from CVD, respiratory, and all cancer, but not lung cancer. PM_2.5-associated risks of CVD and respiratory mortality were similar across PM_2.5 levels, with no evidence of a threshold. Blacks, urban, and younger beneficiaries were most vulnerable to the long-term impacts of PM_2.5 on mortality.

Long-term NO2 exposures and cause-specific mortality in American older adults

BACKGROUND

The impact of long-term exposure to nitrogen dioxide (NO₂) on cause-specific mortality is poorly understood.

OBJECTIVE

To assess mortality risks associated with long-term NO₂ exposure and evaluate confounding of this association.

METHODS

We examined the association between 12-month moving average NO₂ exposure and cause-specific mortality in 14.1 million US Medicare beneficiaries between 2000 and 2008. Associations were examined using age, gender, and race-stratified and state-adjusted Poisson regression models. We assessed the potential for confounding by PM_2.5 and behavioral covariates and unmeasured confounding by decomposing NO₂ into its spatial and spatio-temporal components.

RESULTS

We found significant associations between 12-month NO₂ exposure and increased mortality from all-causes [risk ratio (RR): 1.052; 95% CI: 1.051, 1.054; per 10 ppb], cardiovascular (CVD) (1.133; 95% CI: 1.130, 1.137) and respiratory disease (1.050; 95% CI: 1.044, 1.056), all cancers (1.021; 95% CI: 1.017, 1.025), ischemic heart disease (IHD) (1.221; 95% CI: 1.217, 1.226), cerebrovascular (CBV) disease (1.092; 95% CI: 1.085, 1.100), and for the first time pneumonia (1.275; 95% CI: 1.263, 1.287). Associations generally remained positive and statistically significant after adjustment for PM_2.5 and behavioral factors.

CONCLUSIONS

Our findings provide additional evidence of the increased risk posed by long-term NO₂ exposures on increased mortality from all-causes, CVD, respiratory disease, IHD, CBV, and cancer and provide new evidence of their impact on mortality from pneumonia. Unmeasured confounding of these associations was present, however, demonstrating the need to understand sources of this confounding.

Effects of Personal Exposure to Ambient Fine Particulate Matter on Acute Change in Nocturnal Heart Rate Variability in Subjects Without Overt Heart Disease

The immediate effect within minutes to hours of personal exposure to ambient fine particulate matter (PM2.5) on cardiac autonomic function is limited, particularly at night. Our study aimed to assess the lagged association between personal exposure to PM2.5 and nocturnal heart rate variability. Repeated measures panel study among 21 community adults recruited from a local health clinic during the period of March 1, 2004, to August 31, 2004, in Boston, Massachusetts, in the United States. Ambulatory electrocardiogram and continuous monitoring of personal exposure to PM2.5 and were measured for up to 2 consecutive days. We calculated 5-minute time-specific average PM2.5 exposure for each participant. Mixed-effects models were fit for 5-minute SD of normal-to-normal intervals (SDNN) and 5-minute heart rate in relation to 5-minute PM2.5 exposure lagged in 5-minute intervals up to 4 hours. We found an 8.4% decrease in nocturnal SDNN (95% confidence interval [CI] -11.3% to -5.5%) and a 1.9% increase in nighttime heart rate (95% CI 1.1% to 2.7%) for an interquartile range increase in PM2.5 (13.6 μg/m(3)), after adjusting for confounders. Significant decreases in nocturnal SDNN associated with PM2.5 exposure occurred within 2.5 hours. The largest decrease in nocturnal SDNN of -12.8% (95% CI -16.4 to -9.1%) that was associated with PM2.5 exposure was found with a lag of 25 minutes. Rapid changes in nocturnal heart rate variability associated with personal PM2.5 exposure occurred within the previous 2.5 hours, with the largest effects at 25 minutes, suggesting immediate cardiac autonomic effects of fine particulate exposure.

Modification of the association between lead exposure and amyotrophic lateral sclerosis by iron and oxidative stress related gene polymorphisms

Our objective was to examine whether functional polymorphisms in hemochromatosis (HFE; H63D and C282Y), transferrin (TfC2), and glutathione-s-transferase Pi1 (GSTP1; Ile105Val) genes modify any lead-ALS association. We measured blood lead using atomic absorption spectroscopy and bone lead - a biomarker of cumulative lead exposure - using K-shell-X-ray fluorescence in 100 neurologist-confirmed ALS cases and 194 controls, the latter recruited as part of two separate studies; all subjects lived in New England. Participants were considered variant carriers or wild-type for each polymorphism. To assess effect modification, we included cross-product terms between lead biomarkers and each polymorphism in separate adjusted polytomous logistic regression models. Compared with wild-type, the odds ratio (OR) per 15.6 μg/g patella lead (interquartile range; IQR) was 8.24 (95% CI 0.94-72.19) times greater among C282Y variant carriers, and 0.34 (95% CI 0.15-0.78) times smaller among H63D variant carriers. Results were weaker for tibia lead. Compared with wild-type the OR per 2 μg/dl blood lead (IQR) was 0.36 (95% CI 0.19-0.68) times smaller among H63D variant carriers, and 1.96 (95% CI 0.98-3.92) times greater among GSTP1 variant carriers. In conclusion, we found that HFE and GSTP1 genotypes modified the association between lead biomarkers and ALS. Contrasting modification by the HFE polymorphisms H63D and C282Y may suggest that the modification is not simply the result of increased iron.

Oxidative stress and systemic inflammation as modifiers of cardiac autonomic responses to particulate air pollution

BACKGROUND

The role of oxidative stress and systemic inflammation on the association between personal exposures to ambient fine particulate matter ≤ 2.5 μm in diameter (PM2.5) and cardiac autonomic dysfunction, indicated by reduction in heart rate variability (HRV), has not been examined.

METHODS

We performed a repeated measures study on community adults in a densely populated inner city neighborhood in Boston, Massachusetts. Continuous ambulatory electrocardiogram (ECG) monitoring and personal exposure to PM2.5 were measured for up to two consecutive days. Peripheral blood and spot urine samples were collected at 12-hour intervals for the measurements of markers of inflammation including C-reactive protein (CRP), fibrinogen, white blood cell (WBC) and platelet counts as well as for the analysis of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage.

RESULTS

After adjusting for confounders, we found a pronounced decrease in nighttime standard deviation of normal-to normal intervals (SDNN): an interquartile range (IQR) increase in PM2.5 (13.6 μg/m(3)) was associated with an 8.4% decrease in SDNN (95% CI: -11.3 to -5.5). Compared with the lower eightieth percentile, significantly greater PM2.5 associated nighttime SDNN reductions were observed among subjects in the upper twentieth percentile of 8-OHdG by -25.3%, CRP by -24.9%, fibrinogen by -28.7%, WBC by -23.4%, and platelet counts by -24.0% (all P<0.0001; all P interaction<0.01).

CONCLUSIONS

These data suggest that oxidative stress and systemic inflammation exacerbate the adverse effects of PM2.5 on the cardiac autonomic function even at ambient levels of exposure.

Cumulative lead exposure and age at menopause in the Nurses' Health Study cohort

BACKGROUND

Early menopause has been associated with many adverse health outcomes, including increased risk of cardiovascular disease morbidity and mortality. Lead has been found to be adversely associated with female reproductive function, but whether exposures experienced by the general population are associated with altered age at menopause has not been explored.

OBJECTIVE

Our goal was to assess the association between cumulative lead exposure and age at natural menopause.

METHODS

Self-reported menopausal status and bone lead concentration measured with K-shell X-ray fluorescence-a biomarker of cumulative lead exposure-were obtained from 434 women participants in the Nurses' Health Study.

RESULTS

The mean (± SD) age at natural menopause was 50.8 ± 3.6 years. Higher tibia lead level was associated with younger age at menopause. In adjusted analyses, the average age of menopause for women in the highest tertile of tibia lead was 1.21 years younger (95% CI: -2.08, -0.35) than for women in the lowest tertile (p-trend = 0.006). Although the number of cases was small (n = 23), the odds ratio for early menopause (< 45 years of age) was 5.30 (95% CI: 1.42, 19.78) for women in the highest tertile of tibia lead compared with those in the lowest tertile (p-trend = 0.006). There was no association between patella or blood lead and age at menopause.

CONCLUSIONS

Our results support an association between low-level cumulative lead exposure and an earlier age at menopause. These data suggest that low-level lead exposure may contribute to menopause-related health outcomes in older women through effects on age at menopause.

CITATION

Eum KD, Weisskopf MG, Nie LH, Hu H, Korrick SA. 2014. Cumulative lead exposure and age at menopause in the Nurses' Health Study Cohort. Environ Health Perspect 122:229–234; http://dx.doi.org/10.1289/ehp.1206399

Relation of cumulative low-level lead exposure to depressive and phobic anxiety symptom scores in middle-age and elderly women

BACKGROUND

Different lines of evidence suggest that low-level lead exposure could be a modifiable risk factor for adverse psychological symptoms, but little work has explored this relation.

OBJECTIVE

We assessed whether bone lead--a biomarker of cumulative lead exposure--is associated with depression and anxiety symptoms among middle-age and elderly women.

METHODS

Participants were 617 Nurses' Health Study participants with K-shell X-ray fluorescence bone lead measures and who had completed at last one Mental Health Index 5-item scale (MHI-5) and the phobic anxiety scale of the Crown-Crisp Index (CCI) assessment at mean ± SD age of 59 ± 9 years (range, 41-83 years). With exposure expressed as tertiles of bone lead, we analyzed MHI-5 scores as a continuous variable using linear regression and estimated the odds ratio (OR) of a CCI score ≥ 4 using generalized estimating equations.

RESULTS

There were no significant associations between lead and either outcome in the full sample, but associations were found among premenopausal women and women who consistently took hormone replacement therapy (HRT) between menopause and bone lead measurement (n = 142). Compared with women in the lowest tertile of tibia lead, those in the highest scored 7.78 points worse [95% confidence interval (CI): -11.73, -3.83] on the MHI-5 (p-trend = 0.0001). The corresponding OR for CCI ≥ 4 was 2.79 (95% CI: 1.02, 7.59; p-trend = 0.05). No consistent associations were found with patella lead.

CONCLUSIONS

These results provide support for an association of low-level cumulative lead exposure with increased depressive and phobic anxiety symptoms among older women who are premenopausal or who consistently take postmenopausal HRT.

Prospective cohort study of lead exposure and electrocardiographic conduction disturbances in the Department of Veterans Affairs Normative Aging Study

BACKGROUND

No studies have examined the association between cumulative low-level lead exposure and the prospective development of electrocardiographic conduction abnormalities, which may mediate the association between lead and several cardiovascular end points.

OBJECTIVE

We prospectively examined the association between lead exposure and the development of electrocardiographic conduction abnormalities.

METHODS

We assessed blood lead, bone lead--a biomarker of cumulative lead exposure--measured with K-shell X-ray fluorescence, and electrocardiographic end points among 600 men in the Normative Aging Study who were free of electrocardiographic abnormalities at the time of the baseline ECG. Of these men, we had follow-up data from a second electrocardiogram for 496 men 8.1 (SD = 3.1) years later, on average. We used repeated measures linear regression to analyze change in electrocardiographic conduction timing and logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for developing specific conduction disturbances and adjusted for potential confounders.

RESULTS

Mean (± SD) blood (5.8 ± 3.6), patella bone (30.3 ± 17.7), and tibia bone (21.6 ± 12.0) lead concentrations were similar to those found in samples from the general U.S. population and much lower than those reported in occupationally exposed groups. Compared with those in the lowest tertile of tibia lead, those in the highest had a 7.94-ms (95% CI, 1.42-14.45) increase in heart rate-corrected QT (QTc) interval and a 5.94-ms increase in heart rate-corrected QRS (95% CI, 1.66-10.22) duration > 8 years. Those in the highest tertile of tibia lead also had increased odds of QT prolongation (QTc ≥ 440 msec; OR = 2.53; 95% CI, 1.22-5.25) and JT prolongation (heart rate-corrected JT > 360 msec; OR = 2.53; 95% CI, 0.93-6.91). Results were weaker for patella lead. No associations were identified with blood lead.

CONCLUSIONS

This study suggests that low-level cumulative exposure to lead is associated with worse future cardiac conductivity in the ventricular myocardium, as reflected in QT interval characteristics.

Seasonal and regional contributors of 1-hydroxypyrene among children near a steel mill

Urinary 1-hydroxypyrene (1-OHP) is a biomarker of exposure to polycyclic aromatic hydrocarbons (PAH). Effect of residence on children's PAH exposure was reported among children living near a polluted area. Instead of a snapshot assessment, however, a temporal history of exposure characteristics needs to be assessed in the studies of chronic disease development such as cancer. The urinary 1-OHP measurements were repeated to determine regional effect of ambient air pollution on 1-OHP levels over extended periods. Two sites were chosen: (a) one site located near the steel mill ("nearby" site) and (b) the other site located at a longer distance from the mill ("remote" site). Spot urinary 1-OHP levels were measured from 72 children for 3 consecutive days per month, repeated over 9-month period. Compared with remote site, the nearby site had increased the urinary 1-OHP level by 62.3% [95% confidence interval (95% CI), 39.8-88.3%]. Other statistically significant factors that contributed to the level include sex [16.5% (95% CI, 1.2-34.1%) higher for girls than boys], consumption of charbroiled meat [16.5% (95% CI, 1.1-34.2%) higher], and an increase in PM(10) [10.1% (95% CI, 4.8-15.7%) higher for the interquartile range increment]. Controlling for covariates, the 1-OHP levels were increased in the summer and fall compared with winter. The magnitude of the effects of both seasons had diminished after adjusting for PM(10). This is the first report providing seasonal and regional contributors to environmental PAH exposure, assessed by urinary 1-OHP, with higher 1-OHP levels during summer when ambient pollution was also high.

Cadmium in blood and hypertension

OBJECTIVES

This study is to examine the effect of cadmium exposure on blood pressure in Korean general population.

METHODS

The study population consisted of 958 men and 944 women who participated in the 2005 Korean National Health and Nutrition Examination Survey (KNHANES), in which blood pressure and blood cadmium were measured from each participant.

RESULTS

The mean blood cadmium level was 1.67 microg/L (median level 1.55). The prevalence of hypertension was 26.2%. The blood cadmium level was significantly higher among those subjects with hypertension than those without (mean level 1.77 versus 1.64 microg/dL). After adjusting for covariates, the odds ratio of hypertension comparing the highest to the lowest tertile of cadmium in blood was 1.51 (95% confidence interval 1.13 to 2.05), and a dose-response relationship was observed. Systolic, diastolic, and mean arterial blood pressure were all positively associated with blood cadmium level, and this effect of cadmium on blood pressure was markedly stronger when the kidney function was reduced.

CONCLUSIONS

Cadmium exposures at the current level may have increased the blood pressure of Korean general population.

Paternal work stress and prolonged time to pregnancy

OBJECTIVE

The aim of this study was to explore an association between psychosocial stress at work in married men and their spouses' prolonged time to pregnancy (TTP).

METHODS

All married male workers of a large Korean petrochemical enterprise and their wives fulfilling the selection criteria were included. Main selection criteria were lack of use of contraceptives and experienced pregnancy in recent past. Data were available from 322 couples. Psychosocial stress at work was measured by the effort-reward imbalance questionnaire. Prolonged TTP was measured by the "TTP questionnaire".

RESULTS

After adjustment for confounding effects of demographic and life-style characteristics and benzene exposure, delayed TTP, defined by frequency of first-cycle pregnancy, was associated with one standard deviation (SD) increase of the effort-reward ratio in the chronically stressed group of married men (OR = 0.47; 95% CI = 0.22-0.99) in logistic regression analysis. A similar, but somewhat weaker effect, was found for the overall group (OR = 0.67; 95% CI = 0.47-0.94).

CONCLUSIONS

Paternal stress at work, as measured by effort-reward imbalance, seemed to be associated with a decreased number of conceptions in the first menstrual cycle.

1-Hydroxypyrene as a biomarker of PAH exposure among subjects living in two separate regions from a steel mill

OBJECTIVE

Steel mills are known to be a source of ambient polycyclic aromatic hydrocarbons (PAHs), and increased cancer risk has been reported among neighborhoods previously. In this study, we tried to assess the exposure to PAHs among residents nearby to a large steel mill in Korea by measuring urinary 1-hydroxypyrene (1-OHP).

METHODS

Two separate areas at different distances from a steel mill but on the same wind direction were chosen to evaluate the environmental exposures to polycyclic aromatic hydrocarbons. Three-hundred and fifty children living in the vicinity of steel plant ("nearby" group) and 606 children residing much farther from the factory ("remote" group) participated. Urine was collected on three consecutive days, and questionnaires about exposure to passive smoking and food consumption as well as demographics were obtained. Routine monitoring data of ambient pollutants were obtained and particulate matter less than 10 microm (PM10) was analyzed with multiple regressions to assess the associations with urinary 1-OHP.

RESULTS

The geometric mean concentration of urinary 1-OHP among nearby group (0.048+/-1.878 micromol/mol creatinine, GM+/-GSD) was approximately 1.3 times higher than that among remote group (0.036+/-2.425 micromol/mol creatinine, GM+/-GSD), and using multiple regression techniques, the difference was significant (P<0.0001) after adjusting for confounding variables. When different periods before the sampling of urine were examined, PM10 averages over 2 days, 3 days, and 1 week prior to urine sampling showed significant associations with urinary 1-OHP levels.

CONCLUSION

Our findings are consistent with the interpretation that residents nearby to a steel mill are exposed to PAHs through ambient exposures.

Psychometric properties of the Korean version of the effort–reward imbalance questionnaire: a study in a petrochemical company

OBJECTIVE

To evaluate the criterion validity, factorial validity, and internal consistency of Korean version of effort-reward imbalance (ERI) for the scales of effort, reward, and overcommitment as well as to examine the effect of psychosocial factors on physical and mental illness among petroleum refinery workers in South Korea.

METHODS

The Korean version of ERI questionnaire was constructed using the translation and back-translation technique, and its psychometric properties were explored among 908 male workers in a large petroleum refinery in South Korea in 2002. Cronbach's alpha coefficient was used to test internal consistency. An exploratory factor analysis was conducted on all items of the instrument. Confirmatory factor analyses were conducted on each dimension of effort, reward and overcommitment. Physical and mental health was measured by self-rated health (SF-8). The lowest tertiles of the scores were defined as illness. Multiple logistic regression models were used to test the effect of job stress on the physical and mental health (criterion validity of ERI scales).

RESULTS

The Cronbach's alpha coefficients for effort, reward, and overcommitment were 0.71, 0.86, and 0.75, respectively, indicating satisfactory internal consistency. Exploratory factor analysis found three latent factors, which closely corresponded to the theoretical structure of the ERI model. Acceptable construct validity was shown using confirmatory factor analysis. The highest tertile of effort-reward ratio was significantly associated with physical illness (OR 2.4, 95% CI 1.7-3.6) and mental illness (OR 2.9, 95% CI 2.0-4.2), compared to lower tertiles. Overcommitment was significantly associated with mental illness, but not with physical illness.

CONCLUSIONS

These findings contribute to the validity and reliability of the Korean ERI questionnaire. Importantly, in the context of a rapid change in the labour market, the lack of reciprocity between efforts and rewards at work is strongly associated with self-rated physical and mental health.

Psychometric properties of the Korean version of the job content questionnaire: data from health care workers

OBJECTIVES

To test the validity and reliability of selected scales, namely, decision latitude, psychological job demand, social support, job insecurity, and macro-level decision latitude from the Korean version of the job content questionnaire (K-JCQ), as part of a psychosocial epidemiological study among university hospital workers.

METHODS

K-JCQ was developed by translation and back translation complying with the JCQ usage policy, and its psychometric properties were explored among 338 workers (290 females and 48 males) in a university hospital in Korea. Internal consistency was examined using Cronbach's alpha correlation coefficients. Factorial validity was tested using exploratory factor analysis. Pearson's correlation coefficients were used for test-retest reliability among a subset of 157 workers who responded to a repeat survey. Criterion-related validity was assessed by investigating the effects of the scales on job satisfaction and self-identity through work in multiple regression models.

RESULTS

Cronbach's alpha for all selected scales was higher than 0.6, except for job insecurity (0.53) and macro-level decision authority (0.52), indicating appropriate internal consistency. Correlation coefficients between test and retest scales of decision latitude, psychological job demand, and social support were 0.60, 0.41, and 0.35, respectively. Exploratory factor analysis found three- and four-factor models, i.e., with and without macro-level decision latitude, respectively, closely corresponding to the theoretical constructs. High levels of decision latitude and social support, and low levels of psychological job demand and job insecurity were significantly associated with high level of job satisfaction. Higher self-identity through work was positively related to decision latitude and social support.

CONCLUSIONS

These findings suggest that K-JCQ is valid and reliable for assessing psychosocial job stress among Korean workers. Macro-level decision latitude showed a separate factorial structure and was strongly associated with task-level decision latitude.