Researchers at Rice University in Houston have found a direct correlation between out-of-hospital cardiac arrests and levels of air pollution and ozone. Their work has prompted more CPR training in at-risk communities.
For the new study, the authors analyzed eight years’ worth of data drawn from Houston’s extensive network of air-quality monitors and more than 11,000 concurrent out-of-hospital cardiac arrests (OHCA) logged by Houston Emergency Medical Services (EMS).
They found a positive correlation between OHCAs and exposure to both fine particulate matter (airborne particles smaller than 2.5 micrograms) and ozone.
The researchers found that a daily average increase in particulate matter of 6 micrograms per day over two days raised the risk of OHCA by 4.6 percent, with particular impact on those with pre-existing (and not necessarily cardiac-related) health conditions. Increases in ozone level were similar, but on a shorter timescale: Each increase of 20 parts per billion over one to three hours also increased OHCA risk, with a peak of 4.4 percent. Peak-time risks from both pollutants rose as high as 4.6 percent. Relative risks were higher for men, African-Americans and people over 65.
For the study, OHCA events were defined as cases where EMS personnel performed chest compressions. Ensor and Raun noted the patients died in more than 90 percent of the cases, which occurred more during the hot summer months (55 percent of total cases).
The researchers also looked at the effects of nitrogen dioxide, sulfur dioxide and carbon monoxide levels, none of which were found to impact the occurrence of OHCA.
Ozone standards focus on peak conditions, but some epidemiological studies show that substantial health benefits can also result from reducing ozone at other times, he said. Thus, emission-control strategies aimed solely at achieving regulatory standards may not yield as great a health benefit as strategies that reduce ozone year-round. This research has important implications as states aim to attain national ozone standards. The standards are now set at 75 parts per billion (ppb), but the EPA is considering tightening them to a level in the 60-70 ppb range.
A 2012 study by Raun and Ensor published by Rice’s Baker Institute for Public Policy determined that, overall, the current EPA standard for ozone serves its purpose, while the particulate standard of 35 micrograms per cubic meter does not.
“The bottom-line goal is to save lives,” Ensor said. “We’d like to contribute to a refined warning system for at-risk individuals. Blanket warnings about air quality may not be good enough.
“At the same time, we want to enhance our understanding of the health cost of pollution – and celebrate its continuing reduction.”
SOURCE- Rice University
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