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2 International Journal of Occupational Medicine and Environmental Health

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Factorization methods applied to characterize the sources of volatile organic compounds in Montreal, Quebec

100%

Porada E. , Kousha T.

nr 1

15-39

Objectives The study objective was to assemble emission characteristics of the sources of the ambient volatile organic compounds (VOCs) and to elaborate methods of organizing them into the sources’ chemical profiles. Material and Methods The UNMIX – sensor modeling method from the U.S. Environment Protection Agency (EPA) – was used to process the VOC concentration data acquired over the years 2000–2009 for 175 VOC species in 4 air quality monitoring stations in Montreal, Quebec. Results The method enabled to assess VOC emissions from the typically distributed sources existing in urban environment and VOC occurrences characterizing the local, or point-like, sources. The distributed sources were inextricably associated with hydrocarbons from exhaust, heavier hydrocarbons from contaminated urban soil, fugitive evaporations of gasoline and liquefied petroleum gases (LPG), leakage from the industrial and commercial use of solvents, and the inert, ozone depleting gases permeating urban atmosphere. The sources’ profiles were charted involving 60–120 VOC species per source. Spatial distribution of the sources was examined. Conclusions The UNMIX application and the source profiling methods, by building robust chemical profiles of VOC sources, provided information that can be used to assign the measured VOC emissions to physical sources. This, in turn, provides means of assessing the impact of environmental policies, on one hand, and of industrial activities on the other hand on VOC air pollution.

Air pollution and emergency department visits for conjunctivitis: A case-crossover study

80%

Szyszkowicz M. , Kousha T. , Castner J.

tom 29

nr 3

381-393

Objectives The purpose of this study was to examine the associations between emergency department (ED) visits for conjunctivitis and ambient air pollution levels in urban regions across the province of Ontario, Canada. Material and Methods Information from the National Ambulatory Care Reporting System was used to create time-series records, for the period of April 2004 to December 2011, on emergency department visits of patients suffering from conjunctivitis. A total of 77 439 emergency department visits for conjunctivitis were analyzed. A time-stratified case-crossover design was applied, completed with meta-analysis in order to pool inter-city results. Odds ratio (OR) for an emergency department visit was calculated in different population strata per one-unit increase (one interquartile range – IQR increase in a pollutant’s daily level) while controlling for the impacts of temperature and relative humidity. Results Statistically significant positive results were observed in the female population sample, for nitrogen dioxide (NO₂) exposure lagged 5–8 days, with the highest result for the 7-day lag (OR = 1.035, 95% CI: 1.018–1.052) and for fine particulate matter with a median aerodynamic diameter of less than 2.5 μm ($\text{PM}_\text{2.5}$), for lags 6 and 7 days, with the highest result for lag 7 (OR = 1.017, 95% CI: 1.003–1.031). In the male population sample, statistically significant positive results were observed for NO₂ at lag 5 days (OR = 1.024, 95% CI: 1.004–1.045) and for ozone (O₃), at lags 0–3 and 7 days, with the highest result for lag 0 (OR = 1.038, 95% CI: 1.012–1.056). Also for males, statistically significant results were observed in the case of $\text{PM}_\text{2.5}$ exposure lagged by 5 days (OR = 1.003, 95% CI: 1.000–1.038) and sulfur dioxide (SO₂) exposure lagged by 1 and 2 days (OR = 1.016, 95% CI: 1.000–1.031 and OR = 1.018, 95% CI: 1.002–1.033). Conclusions The findings of this study suggest that there are associations between levels of air pollution and ED visits for conjunctivitis, with different temporal trends and strength of association by age, sex, and season.