Cardiovascular disease cluster linked to pollution

NEW YORK (Reuters Health) - A sudden spate of urgent cardiovascular syndromes resulting in severe chest pain that required emergency department visits among residents of Sydney, Australia, in 2005 has been traced to high solar radiance and ozone levels.

Surveillance data indicated an increase in urgent visits to city hospitals by individuals with chest pain assessed as "imminently or immediately life-threatening on arrival" in April and May 2005, Dr. Robin M. Turner of New South Wales Department of Health in North Sydney and colleagues report in the journal Environmental Health.

Emergency department visits increased from 4.0 per day in 2004 to 5.7 per day for the 8 weeks of April and May 2005.

The researchers compared emergency department visits with daily weather and pollution variables to find an explanation for the sudden peak in urgent cardiovascular syndrome visits.

"Given the known association between environmental factors and cardiovascular disease outcomes, and the unusual extended period of dry, mild, stable weather conditions arising from drought conditions at the time, we hypothesised an environmental cause of the observed increase," the investigators write.

They did, in fact, find an association between environmental factors and increases in urgent cardiovascular disease syndromes requiring emergency care. Specifically, high temperatures increased the risk by 27 percent, high radiation levels increased the risk by 44 percent and high ozone levels increased the risk by 13 percent.

The factors that best explained these correlations were probably of "photochemical origin, given the observed associations with ozone, solar radiation and temperature during that period," Turner and colleagues write.

"Both solar radiation and temperature are important catalysts in photochemical smog reactions that produce ozone and other oxidants," the Sydney investigators point out. The chemical reactions have been associated with various cardiovascular disease manifestations, including irregular heart contractions.

"Temperature and solar radiation were unseasonally high during the outbreak period. The addition of drought and high atmospheric pressure provided favourable conditions for atmospheric stagnation and ozone build-up. The reduced variability in air pressure during the outbreak period provides further support to a stagnation hypothesis," Turner and colleagues conclude.

SOURCE: Environmental Health 2007.