Relationship between low birthweight and air pollution in the city of Sao Paulo, Brazil

OBJECTIVE: Air pollution has been investigated as a potential determinant for low birthweight. The aim of the present study was to study the effect of air pollution on birthweight. METHODS: We analyzed all deliveries by mothers living in the municipality of Sao Paulo, Southeastern Brazil, between 1998 and 2000. We estimated the prevalence of low birthweight according to newborn, mother, and delivery characteristics. Only births occurring in the most central districts of the city were analyzed, totaling 311.735 events. For the evaluation of the effects of air pollution, we excluded preterm and multiple deliveries. Pollutants analyzed were ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), suspended particles (PM10), and carbon monoxide (CO). The effect of maternal exposure to air pollution on birthweight was evaluated using linear and logistic regression. RESULTS: A total of 4.6% of newborns weighed less than 2,500 g at birth. Maternal exposure to CO, PM10, and NO2 during the first trimester of pregnancy was significantly associated with decreased birthweight. CONCLUSIONS: Our results reinforce the notion that maternal exposure to air pollution during the first trimester of pregnancy may contribute to lesser weight gain in the fetus.     

Association between air pollution and low birth weight: a community-based study.

The relationship between maternal exposure to air pollution during periods of pregnancy (entire and specific periods) and birth weight was investigated in a well-defined cohort. Between 1988 and 1991, all pregnant women living in four residential areas of Beijing were registered and followed from early pregnancy until delivery. Information on individual mothers and infants was collected. Daily air pollution data were obtained independently. The sample for analysis included 74,671 first-parity live births were gestational age 37-44 weeks. Multiple linear regression and logistic regression were used to estimate the effects of air pollution on birth weight and low birth weight (< 2,500 g), adjusting for gestational age, residence, year of birth, maternal age, and infant gender. There was a significant exposure-response relationship between maternal exposures to sulfur dioxide (SO2) and total suspended particles (TSP) during the third trimester of pregnancy and infant birth weight. The adjusted odds ratio for low birth weight was 1.11 (95% CI, 1.06-1.16) for each 100 micrograms/m3 increase in SO2 and 1.10 (95% CI, 1.05-1.14) for each 100 micrograms/m3 increase in TSP. The estimated reduction in birth weight was 7.3 g and 6.9 g for each 100 micrograms/m3 increase in SO2 and in TSP, respectively. The birth weight distribution of the high-exposure group was more skewed toward the left tail (i.e., with higher proportion of births < 2,500 g) than that of the low-exposure group. Although the effects of other unmeasured risk factors cannot be excluded with certainty, our data suggests that TSP and SO2, or a more complex pollution mixture associated with these pollutants, contribute to an excess risk of low birth weight in the Beijing population.     

Association between gaseous ambient air pollutants and adverse pregnancy outcomes in Vancouver, Canada

The association between ambient air pollution and adverse health effects, such as emergency room visits, hospitalizations, and mortality from respiratory and cardiovascular diseases, has been studied extensively in many countries, including Canada. Recently, studies conducted in China, the Czech Republic, and the United States have related ambient air pollution to adverse pregnancy outcomes. In this study, we examined association between preterm birth, low birth weight, and intrauterine growth retardation (IUGR) among singleton live births and ambient concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone in Vancouver, Canada, for 1985-1998. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for such effects. Low birth weight was associated with exposure to SO2 during the first month of pregnancy (OR = 1.11, 95% CI, 1.01-1.22, for a 5.0 ppb increase). Preterm birth was associated with exposure to SO2 (OR = 1.09, 95% CI, 1.01-1.19, for a 5.0 ppb increase) and to CO (OR = 1.08, 95% CI, 1.01-1.15, for a 1.0 ppm increase) during the last month of pregnancy. IUGR was associated with exposure to SO2 (OR = 1.07, 95% CI, 1.01-1.13, for a 5.0 ppb increase), to NO2 (OR = 1.05, 95% CI, 1.01-1.10, for a 10.0 ppb increase), and to CO (OR = 1.06, 95% CI, 1.01-1.10, for a 1.0 ppm increase) during the first month of pregnancy. In conclusion, relatively low concentrations of gaseous air pollutants are associated with adverse effects on birth outcomes in populations experiencing diverse air pollution profiles.     

Low birthweight and socioeconomic status,Victoria 1982 to 1986

Abstract: The aim of this study was to evaluate the association between the incidence of low birthweight and socioeconomic status, in particular whether the relationship was different for very low birthweight (< 1500 g) and moderately low birthweight (1500 to 2499 g). The study population was births from 1982 to 1986 to women resident in Victoria (300 704). Data on socioeconomic status were derived from an indicator developed by the Australian Bureau of Statistics from the 1981 census and applied to postcodes. Using the rates of very low birthweight and moderately low birthweight in the highest socioeconomic status decile as the reference value we found that the relative risk for very low birthweight was significantly raised in only the lowest socioeconomic status decile (relative risk = 1.29, 95% confidence interval (CI) 1.17 to 1.42). The relative risk for moderately low birthweight was increased in the two lowest deciles: 1.19 (CI 1.12 to 1.26) and 1.09 (CI 1.01 to 1.17) respectively. Women not married at the time of the birth had a higher rate of low birthweight and were more likely to live in the lower socioeconomic status postcode areas. The relationships between very low birthweight, moderately low birthweight and socioeconomic status were attenuated but still significant when this factor was taken into account. Differences in low birthweight by socioeconomic status decile were not apparent for nonsmoking women. The relationship between smoking and low birthweight was different in the two lowest socioeconomic status deciles: the relative risk of low birthweight in smokers was 2.60 (CI 1.73 to 3.91) compared with a relative risk of 1.64 (CI 1.33 to 2.03) in deciles 3 to 10.     

Prenatal ambient air pollution exposure and small for gestational age birth in the Puget Sound Air Basin

Several studies have identified high concentrations of air pollution as harmful to the developing fetus, but few studies of traffic-derived air pollution and birth outcomes have been conducted in areas of low to moderate air pollution. We identified singleton live births between 1997 and 2005 (N?=?367,046 births) in the Puget Sound Air Basin of Washington State. We estimated nitrogen dioxide (NO₂) exposure using a land use regression model of traffic, PM_2.5 exposure from the nearest community monitor, and proximity to highways/roadways for the residential location of all subjects. Logistic regression estimates of odds ratios (OR) of small for gestational age (SGA) and low birth weight (<2,500 g) among term births were calculated. We observed a modest association between SGA births with increasing quartile of first trimester NO₂ exposure: second (OR?=?1.01, 95 % confidence interval (CI) 0.97, 1.04), third (OR?=?1.06, 95 % CI 1.03, 1.10), and fourth (OR?=?1.08, 95 % CI 1.04, 1.12) (p trend <0.001). We did not observe an association between PM_2.5 and SGA or low birth weight among term births. Our findings suggest that prenatal exposure to traffic-derived air pollutants has a modest effect on fetal growth in a region with low overall air pollutant concentrations. Given the modest associations, future studies in similar settings that maximize the opportunity to address potential residual confounding are needed.     

Atmospheric pollution and chronic respiratory diseases

A national cooperative study was conducted from 1974 to 1976 in twenty-four areas located in six French cities, in order to investigate the relationships of air pollution to ventilatory function and the prevalence of respiratory symptoms. The concentrations of the following pollutants were daily measured: SO2, suspended particulates, NOx. The population included men and women, non manual workers, aged 25 to 59, and children, aged 6 to 10. The respiratory symptoms and other characteristics of the subjects were recorded and their ventilatory function was measured with a dry expirograph. The main results were as following: a) in adults of both sexes, the pollution in SO2 was associated with the prevalence of lower respiratory symptoms. b) in children, it was associated with the prevalence of upper respiratory symptoms. c) in both adults and children, the higher the SO2 concentration, the lower the FEV1. d) no other pollutant was related to respiratory diseases.     

The effects of air pollution on mortality in socially deprived urban areas in Hong Kong, China

BACKGROUND: Poverty is a major determinant of population health, but little is known about its role in modifying air pollution effects. OBJECTIVES: We set out to examine whether people residing in socially deprived communities are at higher mortality risk from ambient air pollution. METHODS: This study included 209 tertiary planning units (TPUs), the smallest units for town planning in the Special Administrative Region of Hong Kong, China. The socioeconomic status of each TPU was measured by a social deprivation index (SDI) derived from the proportions of the population with a) unemployment, b) monthly household income < US$250, c) no schooling at all, d) one-person household, e) never-married status, and f ) subtenancy, from the 2001 Population Census. TPUs were classified into three levels of SDI: low, middle, and high. We performed time-series analysis with Poisson regression to examine the association between changes in daily concentrations of ambient air pollution and daily number of deaths in each SDI group for the period from January 1996 to December 2002. We evaluated the differences in pollution effects between different SDI groups using a case-only approach with logistic regression. RESULTS: We found significant associations of nitrogen dioxide, sulfur dioxide, particulate matter with aerodynamic diameter < 10 mum, and ozone with all nonaccidental and cardiovascular mortality in areas of middle or high SDI (p < 0.05). Health outcomes, measured as all nonaccidental, cardiovascular, and respiratory mortality, in people residing in high SDI areas were more strongly associated with SO(2) and NO(2) compared with those in middle or low SDI areas. CONCLUSIONS: Neighborhood socioeconomic deprivation increases mortality risks associated with air pollution.     

Outdoor air pollution, low birth weight, and prematurity

This study tested the hypothesis, suggested by several recent reports, that air pollution may increase the risk of adverse birth outcomes. This study analyzed all singleton live births registered by the Czech national birth register in 1991 in 67 districts where at least one pollutant was monitored in 1990-1991 (n = 108,173). Maternal exposures to sulfur dioxide (SO(2)), total suspended particles (TSP), and nitrous oxides (NO(x)) in each trimester of pregnancy were estimated as the arithmetic means of all daily measurements taken by all monitors in the district of birth of each infant. Odds ratios of low birth weight (< 2,500 g), prematurity (< 37 weeks of gestation), and intrauterine growth retardation (IUGR; < 10th percentile of birth weight for gestational age and sex) were estimated by robust logistic regression. The median (and 25th and 75th percentile) trimester exposures were 32 (18, 56) microg/m(3) for SO(2); 72 (55, 87) microg/m(3) for TSP; and 38 (23, 59) microg/m(3) for NO(x). Low birth weight (prevalence 5.2%) and prematurity (prevalence 4.8%) were associated with SO(2) and somewhat less strongly with TSP. IUGR was not associated with any pollutant. The effects on low birth weight and prematurity were marginally stronger for exposures in the first trimester, and were not attenuated at all by adjustment for socioeconomic factors or the month of birth. Adjusted odds ratios of low birth weight were 1.20 [95% confidence interval (CI), 1.11-1.30] and 1.15 (CI, 1.07-1.24) for a 50 microg/m(3) increase in SO(2) and TSP, respectively, in the first trimester; adjusted odds ratios of prematurity were 1.27 (CI, 1.16-1.39) and 1.18 (CI, 1.05-1.31) for a 50 microg/m(3) increase in SO(2) and TSP, respectively, in the first trimester. Low gestational age accounted for the association between SO(2) and low birth weight. These findings provide further support for the hypothesis that air pollution can affect the outcome of pregnancy.     

Changes in the registration of stillbirths < 500 g in Canada, 1985–95

We assessed recent temporal trends in the registration of stillbirths in Canada, with particular regard to stillbirths < 500 g. Data from the Statistics Canada live birth and stillbirth databases for the period 1985-95 were used for the study. The primary analysis was restricted to data from 10 of the 12 provinces and territories of Canada. Data from Newfoundland were excluded because birthweight distributions were not available prior to 1990, and data from Ontario were excluded because of concerns about data quality. The proportion of stillbirths < 500 g increased by 47% [95% confidence interval (CI) 32, 63%], from 12.7% of stillbirths with known birthweight in 1985-7 to 18.7% in 1993-5. Similarly, the rate of stillbirths < 500 g increased by 36% [95% CI 21, 53%], from 7.2 to 9.8 per 10,000 total births from 1985-7 to 1993-5. Similar increases in stillbirth rates were not observed in other low birthweight categories. Live births < 500 g increased 53% [95% CI 33, 77%], from 4.6 to 7.0 per 10,000 live births. Some provinces and territories had low rates of stillbirths < 500 g and no increasing trend, whereas other provinces showed higher rates and increases over time. These regional differences were consistent with differences in stillbirth definitions across the provinces and territories of Canada. Spatio-temporal comparisons of crude stillbirth rates are likely to be compromised unless differences and changes in birth registration practices are addressed.     

Respiratory symptoms and spirometric observations in relation to atmospheric pollutants in a sample of urban population

The prevalence of respiratory problems and the ventilatory functions in subjects belonging to three sample areas with different levels of pollution was studied to ascertain if there is any association between air pollutant levels and abnormal ventilatory functions. The predominant activity existing in that area served as the basis for stratification of the city into industrial (Group I), commercial (Group II) and residential (Group III) areas. Ambient air quality data of suspended particulate matter SPM, SO2 and NOx of the three sample areas were measured using standard methods. 216 men included in the study were administered the American Thoracic Society--Division of Lung Diseases ATS-DLD respiratory questionnaire, clinically examined and subjected to routine laboratory investigations. Spirometry and salbutamol reversibility tests were performed as per the ATS guidelines 1991. The mean and peak levels of SPM in the commercial area and the peak levels in the residential area were higher than the National Ambient Air Quality Standards (NAAQS). The mean and peak levels of NOx and SO2 in all the three areas were lower than the NAAQS. A high prevalence of approximately 30-50% of respiratory symptoms was reported in the present study. Respiratory and ventilatory abnormalities were higher in the commercial areas, which are associated with the higher mean and peak levels of SO2 and the peak levels of NOx. The pollution control measures should also aim at the peak levels of pollutants as they have been shown to exacerbate the respiratory symptoms in the present study.     

Association between maternal exposure to ambient air pollutants during pregnancy and fetal growth restriction

Previous research demonstrated consistent associations between ambient air pollution and emergency room visits, hospitalizations, and mortality. Effect of air pollution on perinatal outcomes has recently drawn more attention. We examined the association between intrauterine growth restriction (IUGR) among singleton term live births and sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), and fine particles (PM2.5) present in ambient air in the Canadian cities of Calgary, Edmonton, and Montreal for the period 1985-2000. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for IUGR, based on average daily levels of individual pollutants over each month and trimester of pregnancy after adjustment for maternal age, parity, infant gender, season, and city of residence. A 1 ppm increase in CO was associated with an increased risk of IUGR in the first (OR=1.18; 95% CI 1.14-1.23), second (OR=1.15; 95% CI 1.10-1.19) and third (OR=1.19; 95% CI 1.14-1.24) trimesters of pregnancy, respectively. A 20 ppb increase in NO2 (OR=1.16; 95% CI 1.09-1.24; OR=1.14; 95% CI 1.06--1.21; and OR=1.16; 95% CI 1.09-1.24 in the first, second, and third trimesters) and a 10 mug/m3 increase in PM2.5 (OR=1.07; 95% CI 1.03-1.10; OR=1.06; 95% CI 1.03-1.10; and OR=1.06; 95% CI 1.03-1.10) were also associated with an increased risk of IUGR. Consistent results were found when ORs were calculated by month rather than trimester of pregnancy. Our findings add to the emerging body of evidence that exposure to relatively low levels of ambient air pollutants in urban areas during pregnancy is associated with adverse effects on fetal growth.     

Social inequality in perceived environmental exposures in relation to housing conditions in Germany

In Germany the impact of socioeconomic factors on environmental exposures and adverse housing conditions has been rarely studied up to now. The aim of our study was to assess whether and, if yes, how perceived exposure to noise and air pollution is influenced by socioeconomic status in Germany. We used data from a large-scale population-based survey. In this survey, data on perceived exposure to noise and air pollution and on socioeconomic status and housing conditions were collected on an individual basis. The study population consisted of 7,275 adults aged 17-98 years (40% women), each representing the head of one household. For the association between perceived environmental exposure and social factors confounder-adjusted odds ratios (OR) with 95% confidence intervals were calculated by binary or ordinal logistic regression. In bivariate analyses subjects with non-German nationality, East Germans, respondents with low income, those with lower educational and occupational status, and subjects living in adverse housing conditions were more likely to report being highly exposed. In multivariate analyses high perceived exposure to noise was associated with low household income (OR 1.52 [95% CI 1.13-2.05] lowest versus highest income group). Perceived air pollution exposure was also related to household income (1.67 [1.14-2.44] lower middle versus highest income group). Further associated variables were need for renovation of the house, type of house, and type of neighborhood. This study shows that in Germany, as in other industrial countries, environmental exposures are distributed unequally and that especially economic differences play important roles.     

Birthweight and perinatal mortality among singletons and twins in north-eastern Tanzania

BACKGROUND: Low birthweights as well as high perinatal mortality rates are common in most African populations. Little is known, however, about how low birthweight corresponds with higher mortality rates within African populations. Twins are known to have lower birthweights and higher perinatal mortality rates than singletons. If lower birthweights represent higher perinatal risk per se, small twins within a population with generally lower birthweights should have critically increased risks. METHODS: In total, 15,255 births in a Tanzanian hospital during 1999-2006 were analysed to determine birthweight distribution and examine perinatal mortality rates (including stillbirths and neonatal deaths within 24 hours) by birthweight in twins and singletons. Referral births from outside the district where the hospital was situated were excluded from analysis. RESULTS: The mean birthweight for births within an estimated normal distribution was 3172 g, with a standard deviation of 462 g. The overall perinatal mortality rate was 43.9 per 1000 births (95% confidence interval: 40.7-47.2). Perinatal mortality rates among twins and singletons were 91.0 and 41.1 per 1000 babies respectively, corresponding to a relative risk of 2.2 (95% confidence interval: 1.7-2.8). The birthweight distribution for twins was shifted to lower birthweights. Twins had a generally lower birthweight and an excess of extremely small births as compared to singletons. The increased mortality rate for twins appeared to be independent of birthweight. CONCLUSIONS: The two-fold increased risk of perinatal death for twins was observed across the whole birthweight distribution, and very small twins appeared to have an excess perinatal risk that was almost similar to that of larger twins.     

Risk factors for small-for-gestational age births among infants in Brazil

OBJECTIVE: To assess the risk factors for small-for-gestational-age (SGA) births. METHODS: All live births occurring in the city of Pelotas, Brazil, between October and December 1993 were identified and mothers interviewed soon after delivery. Birthweight was recorded by the maternity staff. Gestational age was obtained from the mothers' recall of their date of last menstrual period. SGA was defined as a birthweight below the 10th percentile for gestational age and sex, according to the reference developed by Williams. Chi-square test and logistic regression were used in the crude and multivariate analysis, respectively. RESULTS: In all, 1082 births were identified. The prevalence of SGA was 13.1%. Even after adjusting for possible confounding variables, the odds ratio for SGA among those infants whose family income was <1 minimum wage was 8.81 (95% CI, 1.12-69.46) times higher than among those for infants with a family income > or = minimum wage. An antenatal care of low quality was associated with an odds ratio of 3.28 (95% CI, 1.09-9.91) for SGA. Short maternal stature and maternal smoking during pregnancy were also associated with SGA births. CONCLUSIONS: Low socioeconomic status, maternal smoking during pregnancy, maternal height and an antenatal care of low quality are the main risk factors for SGA births.     

Influences of study design and location on the relationship between particulate matter air pollution and birthweight

A large number of studies have identified a relationship between particulate matter air pollution and birthweight. Although reported associations are small and varied, they have been identified in studies from places around the world. Exposure assignment, covariates and study inclusion criteria vary among studies. To examine the effect of these and other study characteristics on associations between particulate matter and birthweight, US birth records for singletons delivered at 40 weeks gestation in 2001-03 during the months of March, June, September and December were linked to quarterly estimates of pollution exposure, both particulate matter exposure and exposure to multiple pollutants, by county of residence and month of birth. Annual, 9-month and trimester-specific exposures were assigned. Among births linked to particulate matter exposure there was a small association between coarse particle exposure and birthweight (beta -13 g per 10 microg/m(3) increase [95% CI -18.3 g, -7.6 g]) after controlling for maternal factors; this association was attenuated slightly and remained statistically significant after further adjustment for contextual factors, year of birth, region, or urban-rural status. The associations were slightly weaker among births linked to multiple pollutant exposure than among births linked to just particulate matter exposure. The association varied markedly by region, ranging from a decrement of 43 g per 10 microg/m(3)[95% CI -58.6 g, -27.6 g] in the north-west to a null association in the south-west. Trimester findings were smaller, yet remained significant and varied regionally. The association between fine particle exposure and birthweight varied considerably, with an overall small positive association that became null after control for region. This study found that wide regional differences in association may contribute to the varied published findings. The association between coarse particle exposure and birthweight appeared robust, if small; fine particles had no overall association with birthweight.     

Urban air pollution and lung cancer in Stockholm

We conducted a population-based case-control study among men 40-75 years of age encompassing all cases of lung cancer 1985-1990 among stable residents of Stockholm County 1950-1990. Questionnaires to subjects or next-of-kin (primarily wives or children) elicited information regarding smoking and other risk factors, including occupational and residential histories. A high response rate (>85%) resulted in 1,042 cases and 2,364 controls. We created retrospective emission databases for NOx/NO2 and SO2 as indicators of air pollution from road traffic and heating, respectively. We estimated local annual source-specific air pollution levels using validated dispersion models and we linked these levels to residential addresses using Geographical Information System (GIS) techniques. Average traffic-related NO2 exposure over 30 years was associated with a relative risk (RR) of 1.2 (95% confidence interval 0.8-1.6) for the top decile of exposure, adjusted for tobacco smoking, socioeconomic status, residential radon, and occupational exposures. The data suggested a considerable latency period; the RR for the top decile of average traffic-related NO2 exposure 20 years previously was 1.4 (1.0-2.0). Little association was observed for SO2. Occupational exposure to asbestos, diesel exhaust, and other combustion products also increased the risk of lung cancer. Our results indicate that urban air pollution increases lung cancer risk and that vehicle emissions may be particularly important.     

Traffic-related air pollution and risk of preterm birth in the San Joaquin Valley of California

PurposeTo evaluate associations between traffic-related air pollution during pregnancy and preterm birth in births in four counties in California during years 2000 to 2006.MethodsWe used logistic regression to examine the association between the highest quartile of ambient air pollutants (carbon monoxide, nitrogen dioxide, particulate matter <10 and 2.5 μm) and traffic density during pregnancy and each of five levels of prematurity based on gestational age at birth (20–23, 24–27, 28–31, 32–33, and 34–36 weeks) versus term (37–42 weeks). We examined trimester averages and the last month and the last 6 weeks of pregnancy. Models were adjusted for birthweight, maternal age, race/ethnicity, education, prenatal care, and birth costs payment. Neighborhood socioeconomic status (SES) was evaluated as a potential effect modifier.ResultsThere were increased odds ratios (ORs) for early preterm birth for those exposed to the highest quartile of each pollutant during the second trimester and the end of pregnancy (adjusted OR, 1.4–2.8). Associations were stronger among mothers living in low SES neighborhoods (adjusted OR, 2.1–4.3). We observed exposure–response associations for multiple pollutant exposures and early preterm birth. Inverse associations during the first trimester were observed.ConclusionsThe results confirm associations between traffic-related air pollution and prematurity, particularly among very early preterm births and low SES neighborhoods.     

Do socioeconomic characteristics modify the short term association between air pollution and mortality? Evidence from a zonal time series in Hamilton,Canada

STUDY OBJECTIVE: To assess the short term association between air pollution and mortality in different zones of an industrial city. An intra-urban study design is used to test the hypothesis that socioeconomic characteristics modify the acute health effects of ambient air pollution exposure. DESIGN: The City of Hamilton, Canada, was divided into five zones based on proximity to fixed site air pollution monitors. Within each zone, daily counts of non-trauma mortality and air pollution estimates were combined. Generalised linear models (GLMs) were used to test mortality associations with sulphur dioxide (SO(2)) and with particulate air pollution measured by the coefficient of haze (CoH). MAIN RESULTS: Increased mortality was associated with air pollution exposure in a citywide model and in intra-urban zones with lower socioeconomic characteristics. Low educational attainment and high manufacturing employment in the zones significantly and positively modified the acute mortality effects of air pollution exposure. DISCUSSION: Three possible explanations are proposed for the observed effect modification by education and manufacturing: (1) those in manufacturing receive higher workplace exposures that combine with ambient exposures to produce larger health effects; (2) persons with lower education are less mobile and experience less exposure measurement error, which reduces bias toward the null; or (3) manufacturing and education proxy for many social variables representing material deprivation, and poor material conditions increase susceptibility to health risks from air pollution.     

Effect of short-term exposure to low levels of SO2 and NOx on pulmonary function and methacholine and allergen bronchial sensitivities in asthmatic children

Air pollution is an inevitable consequence of industrialization. Continuous exposure to air pollution may cause or trigger respiratory allergic diseases. This study was designed to evaluate whether short-term, 5-min exposures to low levels of sulfur dioxide (SO2) and nitrogen oxides (NOx) influence pulmonary function and increase bronchial sensitivity to methacholine and specific allergens. Five male and 1 female mite-sensitive asthmatic children (mean age 12 y) were studied during symptom-free periods. Pulmonary function tests were conducted after breathing 5, 15, 35, 65, and 105 breaths of compressed polluted air, which was collected from the Lin-Sun S. Road tunnel in Taipei city. Concentrations of SO2 and NOx were 70-120 ppb and 450-500 ppb, respectively, and were 6-fold and 20-fold, respectively, higher than those of ambient air. Methacholine and mite allergen bronchial challenges were completed after 105 breaths of polluted air were inhaled. No difference in pulmonary function was noted after polluted air and ambient air were inhaled, and the methacholine and allergen sensitivities of airways were not increased after polluted air was inhaled. The authors concluded that short-term exposures to low concentrations of SO2 and NOx did not affect the lung function and did not increase bronchial sensitivity to methacholine and allergen.     

Does income inequality modify the association between air pollution and health?

BACKGROUND: It has been hypothesized that socioeconomic status may act as an effect modifier of the association between air pollution and health. In this study, we investigated whether income inequality may modify the association between fine particulate pollution and self-reported health. METHODS: We combined several different sources of data. Demographic and socio-economic data, at the individual level, were drawn from the 2001 US Behavioral Risk Factor Surveillance System (BRFSS). County-level particulate pollution data for the year 2001 were provided by the US Environmental Protection Agency. State-level income inequality was measured by the Gini index using US census data from the year 2000. We used a hierarchical logistic regression to model the association between general self-reported health and fine particulate pollution accounting for income inequality as an effect modifier and controlling for the usual confounders. RESULTS: We found that when income inequality is low (10th percentile of the Gini distribution), the odds of reporting fair or poor health for a 10microg/m3 increase in particulate pollution is 1.34 (95% confidence interval 1.21-1.48). The analogous odds ratio for higher income inequality (60th percentile of the Gini distribution) is 1.11 (95% confidence interval 1.06-1.16). CONCLUSIONS: Income inequality was found to be an effect modifier of the association between general self-reported health and particulate pollution. However, these findings challenged our hypothesis that people living in higher income inequality areas are more vulnerable to the impact of air pollution. We discuss the factors driving these results.