Little attention has been devoted to the effects on children's respiratory health of exposure to sulphur dioxide (SO2) in ambient air from local industrial emissions. Most studies on the effects of SO(2) have assessed its impact as part of the regional ambient air pollutant mix.
To examine the association between exposure to stack emissions of SO(2) from petroleum refineries located in Montreal's (Quebec) east-end industrial complex and the prevalence of active asthma and poor asthma control among children living nearby.
The present cross-sectional study used data from a respiratory health survey of Montreal children six months to 12 years of age conducted in 2006. Of 7964 eligible households that completed the survey, 842 children between six months and 12 years of age lived in an area impacted by refinery emissions. Ambient SO(2) exposure levels were estimated using dispersion modelling. Log-binomial regression models were used to estimate crude and adjusted prevalence ratios (PRs) and 95% CIs for the association between yearly school and residential SO(2) exposure estimates and asthma outcomes. Adjustments were made for child's age, sex, parental history of atopy and tobacco smoke exposure at home.
The adjusted PR for the association between active asthma and SO(2) levels was 1.14 (95% CI 0.94 to 1.39) per interquartile range increase in modelled annual SO(2). The effect on poor asthma control was greater (PR=1.39 per interquartile range increase in modelled SO(2) [95% CI 1.00 to 1.94]).
Results of the present study suggest a relationship between exposure to refinery stack emissions of SO(2) and the prevalence of active and poor asthma control in children who live and attend school in proximity to refineries.
In Canada, the Canadian Council of Ministers for the Environment (CCME) is currently engaged in a process to determine how best to reduce air emissions from oil refineries. The National Framework for Petroleum Refineries Emissions Reduction (NFPRER) is being developed with the input of stakeholders, including nongovernment organizations (NGOs), industry, and regulatory jurisdictions. One component of this framework is the development of a tool to prioritize emissions for reduction based on estimated health impacts. HEIDI II (Health Effects Indicators Decision Index II) is a spreadsheet-based model that prioritizes a series of carcinogenic and noncarcinogenic air toxicicants and criteria air contaminants commonly emitted from Canadian oil refineries. A generic meteorological dispersion model was applied to reported annual emissions data for each of Canada's 20 refineries. Photodegradation rates and ambient levels of each substance were accounted for, and air concentrations were calculated for 20 geographic zones around each refinery. These were coupled to toxicity data derived mainly from Health Canada and the U.S. Environmental Protection Agency (EPA), and applied to target populations of children, adults and seniors. HEIDI II predicts incidence of relevant disease endpoints from each substance emitted, except for benzene, toluene, ethylbenzene, and xylene (BTEX) and polycyclic aromatic hydrocarbons (PAH), which were treated as chemical mixtures. Rankings were based on predicted case incidence or the application of a common health impact metric, disability-adjusted life years (DALYs), to the predicted incidence. Using the DALY approach, priority rankings can be made within each of the chemical classes, or across all three classes together. HEIDI II incorporates several switches that allow the user to investigate alternate scenarios based on stack height, average daily sunlight hours (for calculating photodegradation), and the possibility of emissions below regulatory reporting thresholds.
Little is known about the respiratory effects of short-term exposures to petroleum refinery emissions in young children. This study is an extension of an ecologic study that found an increased rate of hospitalizations for respiratory conditions among children living near petroleum refineries in Montreal (Canada).
We used a time-stratified case-crossover design to assess the risk of asthma episodes in relation to short-term variations in sulfur dioxide levels among children 2-4 years of age living within 0.5-7.5 km of the refinery stacks. Health data used to measure asthma episodes included emergency department (ED) visits and hospital admissions from 1996 to 2004. We estimated daily levels of SO2 at the residence of children using a) two fixed-site SO2 monitors located near the refineries and b) the AERMOD (American Meteorological Society/Environmental Protection Agency Regulatory Model) atmospheric dispersion model. We used conditional logistic regression to estimate odds ratios associated with an increase in the interquartile range of daily SO2 mean and peak exposures (31.2 ppb for AERMOD peaks). We adjusted for temperature, relative humidity, and regional/urban background air pollutant levels.
The risks of asthma ED visits and hospitalizations were more pronounced for same-day (lag 0) SO2 peak levels than for mean levels on the same day, or for other lags: the adjusted odds ratios estimated for same-day SO2 peak levels from AERMOD were 1.10 [95% confidence interval (CI), 1.00-1.22] and 1.42 (95% CI, 1.10-1.82), over the interquartile range, for ED visits and hospital admissions, respectively.
Short-term episodes of increased SO2 exposures from refinery stack emissions were associated with a higher number of asthma episodes in nearby children.
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