The Higher The Ozone Levels The Higher Cardiovascular Deaths Due To High Temperatures Are

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Main Category: Cardiovascular / Cardiology
Also Included In: Stroke;  Water - Air Quality / Agriculture;  Respiratory / Asthma
Article Date: 22 Nov 2007 - 0:00 PST

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Ozone may well be the link between a higher risk of heart disease or stroke death due to high temperatures, according to an article in Occupational and Environmental Medicine (BMJ).

The authors based their findings on a population of nearly 100 million citizens in 95 parts of the United States during the period June-September (the hottest months). All the people were already part of the National Mortality and Air Pollution Study (NMMAPS) - a study investigating health and weather pollution during 1987-2000.

4 million heart attacks or strokes occurred during this time. After plotting daily deaths against variations in temperature during one day, they discovered that the common link was ozone. The higher the ozone levels were the higher were the risks of cardiovascular and stroke deaths due to high temperatures.

Average daily temperatures ranged from 20-40 degrees Centigrade, while ozone levels ranged from a daily average of 36.74 ppb (parts per billion) to 142.85 ppb. A 10 degree temperature rise within one day was linked to a 1% rise in heart disease or stroke at the lowest ozone level and an 8% heart disease or stroke rise for the highest level.

Ozone, a chemical pollutant, is strongly tied to weather conditions, particularly the quantity of ultraviolet light in the atmosphere, explain the researchers. A reaction between volatile organic compounds, nitrogen oxides, and oxygen in sunlight generate ozone.

It is conceivable, say the authors, that temperature and ozone are notching up cardiovascular mortality figures. As exposure to ozone affects our airways and autonomic nervous system, it makes us more susceptible to the effects of variations in temperature, they write.

When temperatures are high, public health warnings should include details on ozone levels, the researchers suggest.

The writers add that as the world heats up as a result of global warming, elevated temperatures and the impact of ozone will most likely increase.

"Ozone modifies associations between temperature and cardiovascular mortality: analysis of the NMMAPS data"
Dr Cizao Ren et al
Online First Occup Environ Med 2007
doi: 10.1136/oem.2007.033678
http://oem.bmj.com

Written by - Christian Nordqvist
Copyright: Medical News Today
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