Air pollution could double risk of hospitalization of elders for pneumonia, a Canadian study suggests. Pollutants from car exhaust and industrial air pollution were the focus of the study.
"We postulate that long-term exposure to air pollution may have increased individuals' susceptibility to pneumonia by interfering with innate immune defenses designed to protect the lung from pathogens," lead investigator Dr. Mark Loeb, of McMaster University in Ontario, said in a news release from the American Thoracic Society.
The researchers had set out "to assess the effect of long-term exposure to ambient
nitrogen dioxide, sulfur dioxide, and fine particulate matter
with diameter equal to or smaller than 2.5 µm (PM2.5
on hospitalization for community-acquired pneumonia in older
"We enrolled 345 hospitalized patients
aged 65 years or more for community-acquired pneumonia and 494
control participants, aged 65 years and more, randomly selected
from the same community as cases from July 2003 to April 2005.
Health data were collected by personal interview. Annual average
levels of nitrogen dioxide, sulfur dioxide, and PM2.5
the study period were estimated," the scientists reported in the Jan. 1 issue of the American Journal of Respiratory and Critical Care Medicine.
Breathing two air pollutants for more than 12 months was associated with a doubling in risk of hospitalization from pneumonia — a leading cause of sickness and death among older adults.
"What we found was that individuals who developed community-acquired pneumonia were more likely to have long-term exposure to nitrogen dioxide [from vehicle exhaust] and they were twice more likely to be hospitalized," said principal investigator Dr. Mark Loeb, an infectious disease specialist at McMaster.
The team also looked at another pollutant known as fine particulate matter of less than 2.5 micrometres, which comes mainly from smokestacks at industrial plants. The study took place in Hamilton's north end, where there is an industrial steel-making complex.
Using data from air-quality monitoring stations, the researchers found those with long-term exposure to fine particulate matter showed 2.26 times the risk of hospitalization with pneumonia, CBC News reported.
Exposure to another air pollutant, sulphur dioxide, was not associated with increased risk of hospitalization.
It could be that exposure to pollutants increases susceptibility to severe pneumonia — which is most often caused by a bacterial infection — by interfering with immune system defences that protect the lungs.
The findings highlight how long-term exposure to air pollution can affect respiratory infections, the researchers said. Previously, air pollution has been recognized as a risk factor for exacerbating asthma and chronic pulmonary disease.
"It also emphasizes the need to monitor emissions from vehicles, given that ground level [nitrogen dioxide] is derived predominantly from traffic," the study's authors concluded.