MedWire News: For people with respiratory diseases such as asthma and those with cardiovascular disorders, a rise in levels of large air pollutants does not increase their risk of needing hospital treatment, research shows.
Many studies have shown that increases in concentrations of air pollutants measuring 2.5 µm or less are associated with an increased risk of respiratory and cardiovascular problems, and even death, explain Roger Peng, from Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, USA, and colleagues.
But they add that evidence regarding the health risks associated with increases in pollution particles measuring more than 2.5 µm, such as dust from agricultural activities and industry, is limited.
To investigate further, the team compared pollution measurements with hospital admission rates for respiratory and cardiovascular diseases in 108 US counties between 1999 and 2005.
During this time, there were 1.4 million hospital admissions for respiratory disorders and 3.7 million admissions for cardiovascular disease.
The researchers found that, overall, a 10-µg/m3 increase in pollution particles on any given day was associated with a 0.36% increase in hospital admissions for cardiovascular disease and a 0.33% increase in admissions for respiratory diseases.
However, after accounting for increases in pollution particles measuring less than 2.5 µm, the team found no evidence to show that increases in larger pollution particles were associated with hospital admissions for these disorders.
The researchers conclude in the Journal of the American Medical Association: "After adjustment for particulate matter measuring less than 2.5 µm in diameter, there were no statistically significant associations between coarse particulates and hospital admissions for cardiovascular and respiratory diseases."
They add: ""Nevertheless, we recommend that these findings be considered when the National Ambient Air Quality Standard for particulate matter is next reviewed, and that the monitoring of [large particulate matter] continue so that further studies can be performed."