Epidemiologic studies have reported associations between fine particulate air pollution and cardiovascular mortality or hospitalization for cardiac events. However the evidence regarding the association between air pollution and acute cardiac events, such as out-of-hospital cardiac arrest, is inconsistent. We investigated the association between particulate matter (PM) air pollution and out-of-hospital cardiac arrest using a case-crossover study of adults (age, 35+ years) in Melbourne, Australia. We included 8434 cases identified through the Victorian Cardiac Arrest Registry from 2003 through 2006. We excluded arrests with an obvious preceding noncardiac event such as trauma, poisoning, or drowning, leaving only those events that were presumed to have cardiac etiology. Air pollution concentrations obtained from a central monitoring site were used for day of the arrest and for lag 1, lag 2, and lag 3, including the average lag 0-1. An interquartile range increase of 4.26 microg/m3 in PM2.5 over 2 days (lag 0-1) was associated with an increase in risk for an out-of-hospital cardiac arrest of 3.6% (95% confidence interval = 1.3% to 6.0%). PM10 and carbon monoxide also showed associations, but not as strong as for PM2.5. Longer lag periods did not show such strong relationships. There was no association of these cardiac events with ozone, sulfur dioxide, or nitrogen dioxide in any lag period. Individuals age 65-74 years old were most susceptible to PM2.5 exposure, while those 75 years and older had the lowest risk. These findings support an association between daily average PM2.5 concentrations and an increased risk of out-of-hospital cardiac arrests.

Objectives The aim of this study was to investigate the association between high ambient temperature and acute work-related injury, expanding on previous research in this area. Specifically we examined the relationship between both daytime and overnight temperatures and injury risk and disentangled physically demanding occupational exposures from exposure to outdoor working conditions. Methods A time-stratified case-crossover study design was used to examine the association between ambient temperatures and acute work-related injuries in Melbourne, Australia, 2002–2012, using workers’ compensation claims to identify work-related injuries. The relationship was assessed for both daily maximum and daily minimum temperatures using conditional logistic regression. Results Significant positive associations between temperature and acute work-related injury were seen for younger workers (<25 years), with the odds of injury increasing by 1% for each 1 °C increase in daily minimum temperature, and by 0.8% for each 1 °C increase in daily maximum temperature. Statistically significant associations were also observed between daily maximum temperature and risk of injury for workers employed in the highest strength occupations and for male workers, and between daily minimum temperature and injury for all cases combined, female workers, workers aged 25–35 and ≥55 years, "light" and "limited" physical demand groups, and "in vehicle or cab" and "regulated indoor climate" workplace exposure groups. Conclusions Young workers, male workers and workers engaged in heavy physical work are at increased risk of injury on hot days, and a wider range of worker subgroups are vulnerable to injury following a warm night. In light of climate change projections, this information is important for informing injury prevention strategies.