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Background and aims: Prenatal chemical exposure has frequently been associated with reduced fetal growth although results have been inconsistent. Most studies associate single pollutant exposure to this health outcome, even though this does not reflect real life situations as humans are exposed to many pollutants during their life time. The objective of this study is to investigate the association between prenatal exposure to a mixture of persistent environmental chemicals and birth weight using multipollutant models. Methods: We combined exposure biomarker data measured in cord blood samples of 1579 women from four Flemish birth cohorts collected over a 10 years’ time period. The common set of available and detectable exposure measures in these cohorts are three polychlorinated biphenyls (PCB) congeners (138, 153 and 180), hexachlorobenzene (HCB), dichlorodiphenyldichloroethylene (p,p’-DDE) and the metals cadmium and lead. Multiple linear regression (MLR), Bayesian Information Criterion (BIC), penalized regression using minimax concave penalty (MCP) and Bayesian Adaptive Sampling (BAS) were applied to assess the influence of multiple pollutants in a single analysis on birth weight, adjusted for a priori selected covariates. Results: In the pooled dataset, a median (P25-P75) birth weight and gestational age of 3420 (3140–3700) grams and 39 (39–40) weeks was observed respectively. The median contaminant levels in cord blood were: 15.8, 26.5, 18.0, 16.9 and 91.5 ng/g lipid for PCB 138, PCB 153, PCB 180, HCB and p,p’-DDE, respectively, 0.075 µg/L for cadmium and 9.7 µg/L for lead. According to the applied statistical methods for multipollutant assessment, p,p’-DDE and PCB 180 were most consistently associated with birth weight. In addition, PCB 153 was selected when applying MCP and BAS. An inverse association with birth weight was found for the PCB congeners, while an increased birth weight was observed for elevated levels of p,p’-DDE. Conclusions: Assessing the health risk of combinations of exposure biomarkers reflects better real-world situations and thereby allows more effective risk assessment. Our results add to the existing evidence based on detrimental effects of PCBs on birth weight and indicate a possible increase in birth weight due to p,p’-DDE (while correcting for PCBs).

We evaluated the short-term effect of mixtures of ambient air pollutants on respiratory and circulatory morbidity in four Colombian cities. Daily Emergency Department (ED) visit records for respiratory and circulatory selected diagnosis and daily concentrations for six criteria air pollutant were obtained in four of the five major cities in Colombia: Bucaramanga, Bogota, Cali, and Medellin during 2011–2014. Using conditional Poisson time series analysis with fixed effects, we assessed the effect of air pollutants on health outcomes using single-pollutant, two-pollutant and specific mixtures-of-pollutant models controlling for meteorology and time trends. The percentages of change in the rate of ED visits and their 95% confidence interval were estimated for the joint effect of pollutants. In single-pollutant models increases in gases concentrations were associated with increases in ED visits for respiratory and circulatory diseases. The two-pollutant models for respiratory diseases showed that the effect of NO 2 alone (% change 2.86 95% CI 1.87–3.85) is higher than the joint effect of any of its combinations except for its combination with SO 2 (% change 3.05 95%CI 1.04–5.05). The two-pollutant models for circulatory diseases showed synergistic effects between NO 2 and PM 2.5 (% change 2.13 95%CI 0.001–4.26). Specific mixtures models showed that the mixture of "traffic-related pollutants" has the higher joint effect on circulatory morbidity and respiratory morbidity. The results show the dominant effect of NO 2 in air pollution mixtures on respiratory and circulatory morbidity, and the synergistic effect of NO 2 and SO 2 in air pollution mixtures on respiratory morbidity. Image 1 • Multipollutant analyses of air pollutant effects is limited in developing countries. • We assessed short-term joint effect of mixtures in a tropical developing country. • We found a dominant effect of NO 2 in air pollution mixtures on morbidity. • There is evidence of synergistic effect NO 2 and SO 2 on respiratory morbidity. • Some mixtures effects are well represented by single-pollutant effects. [ABSTRACT FROM AUTHOR]

Background Recent reports have suggested that air pollution mixtures represented by nitrogen dioxide (NO 2 ) may have effects on human health, which are independent from those of particulate matter mass. We evaluate the association between NO 2 and daily mortality among elderly using one- and multipollutant models. Methods This study was a daily time series of non-accidental and cause-specific mortality among the elderly living in São Paulo, Brazil, between 2000 and 2011. Effects of NO 2 , particulate matter smaller than 10 µm (PM10), carbon monoxide (CO) and ozone (O 3 ) were estimated in Poisson generalized additive models. The single lag effect at lags 0 and 1 days and the cumulative effect from 0 to lag 10 days were evaluated in one-, two-, three- and four-pollutant models. The cumulative risk index (CRI) recently proposed to analyze associations with health of multiple correlated pollutants was additionally estimated for each multipollutant model. Results An association between NO 2 , PM10, CO and O 3 exposures and non-accidental and cause-specific deaths was found in one-pollutant models. NO 2 effects remained significant in multipollutant models for non-accidental and circulatory deaths. The estimated CRIs suggested that circulatory deaths were mainly associated with NO 2 , and respiratory deaths mainly with CO and O 3 , regardless the lag. For non-accidental deaths, multipollutant models were associated with the highest CRI, with the main pollutants depending on the chosen lag. Conclusions The results suggest that air pollution mixtures represented by NO 2 have an effect on non-accidental and circulatory mortality, which is independent from PM10, CO and O 3 . The CRI was always larger than the risks associated with single pollutants. [ABSTRACT FROM AUTHOR]

Multipollutant models are frequently used to differentiate roles of multiple pollutants in epidemiologic studies of ambient air pollution. In the presence of differing levels of measurement error across pollutants under consideration, however, they can be biased and as misleading as single-pollutant models. Their appropriate interpretation depends on the relationships among the pollutant measurements and the outcomes in question. In situations where two or more pollutant variables may be acting as surrogates for the etiologic agent(s), multipollutant models can help identify the best surrogate, but the risk estimates may be influenced by inclusion of a second variable that is not itself an independent risk factor for the outcome in question. In this paper, these issues will be illustrated in the context of an ongoing study of emergency visits in Atlanta. Emergency department visits from 41 of 42 hospitals serving the 20-county Atlanta metropolitan area for the period 1993–2004 (n=10,206,389 visits) were studied in relation to ambient pollutant levels, including speciated particle measurements from an intensive monitoring campaign at a downtown station starting in 1998. Relative to our earlier publications, reporting results through 2000, the period for which the speciated data are available is now tripled (6 years in length). Poisson generalized linear models were used to examine outcome counts in relation to 3-day moving average concentrations of pollutants of a priori interest (ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, oxygenated hydrocarbons, PM10, coarse PM, PM2.5, and the following components of PM2.5: elemental carbon, organic carbon, sulfate, and water-soluble transition metals). In the present analysis, we report results for two outcome groups: a respiratory outcomes group and a cardiovascular outcomes group. For cardiovascular visits, associations were observed with CO, NO2, and PM2.5 elemental carbon and organic carbon. In multipollutant models, CO was the strongest predictor. For respiratory visits, associations were observed with ozone, PM10, CO, and NO2 in single-pollutant models. In multipollutant models, PM10 and ozone persisted as predictors, with ozone the stronger predictor. Caveats and considerations in interpreting the multipollutant model results are discussed.Journal of Exposure Science and Environmental Epidemiology (2007) 17, S29–S35; doi:10.1038/sj.jes.7500625 [ABSTRACT FROM AUTHOR]

Prenatal chemical exposure has frequently been associated with reduced fetal growth although results have been inconsistent. Most studies associate single pollutant exposure to this health outcome, even though this does not reflect real life situations as humans are exposed to many pollutants during their life time. The objective of this study is to investigate the association between prenatal exposure to a mixture of persistent environmental chemicals and birth weight using multipollutant models. We combined exposure biomarker data measured in cord blood samples of 1579 women from four Flemish birth cohorts collected over a 10 years' time period. The common set of available and detectable exposure measures in these cohorts are three polychlorinated biphenyls (PCB) congeners (138, 153 and 180), hexachlorobenzene (HCB), dichlorodiphenyldichloroethylene (p,p' -DDE) and the metals cadmium and lead. Multiple linear regression (MLR), Bayesian Information Criterion (BIC), penalized regression using minimax concave penalty (MCP) and Bayesian Adaptive Sampling (BAS) were applied to assess the influence of multiple pollutants in a single analysis on birth weight, adjusted for a priori selected covariates. In the pooled dataset, a median (P25-P75) birth weight and gestational age of 3420 (3140–3700) grams and 39 (39–40) weeks was observed respectively. The median contaminant levels in cord blood were: 15.8, 26.5, 18.0, 16.9 and 91.5 ng/g lipid for PCB 138, PCB 153, PCB 180, HCB and p,p' -DDE, respectively, 0.075 µg/L for cadmium and 9.7 µg/L for lead. According to the applied statistical methods for multipollutant assessment, p,p' -DDE and PCB 180 were most consistently associated with birth weight. In addition, PCB 153 was selected when applying MCP and BAS. An inverse association with birth weight was found for the PCB congeners, while an increased birth weight was observed for elevated levels of p,p' -DDE. Assessing the health risk of combinations of exposure biomarkers reflects better real-world situations and thereby allows more effective risk assessment. Our results add to the existing evidence based on detrimental effects of PCBs on birth weight and indicate a possible increase in birth weight due to p,p' -DDE (while correcting for PCBs). [ABSTRACT FROM AUTHOR]