These findings may help regulators identify which particles are the most important to control from vehicles, factories and fuels.
“A better understanding of what particles in the mixture are most harmful would aid decision makers in developing the most effective policies to protect human health,” said Michelle Bell, a Yale University environmental health scientist.
Inhaling metal and carbon particles may be a risk factor for respiratory problems in children as young as two years old, Columbia University researchers found in a recent study, released this month in the American Journal of Respiratory and Critical Care Medicine.
“We have evidence linking nickel, vanadium and elemental carbon in the air to wheeze and cough in inner city children,” said Dr. Rachel Miller, an allergist and immunologist and co-deputy director of the Columbia University Center for Children’s Environmental Health.
The researchers followed more than 700 children between birth and two years of age living in northern Manhattan and the south Bronx. Every three months, parents filled out a questionnaire about respiratory symptoms. The study controlled for factors such as seasonal trends, ethnicity and exposure to tobacco smoke.
After comparing the questionnaire results with weekly pollutant data at several sites in the community, the researchers found that children exposed to nickel and vanadium were more likely to wheeze. Exposure to carbon particles, a byproduct of diesel exhaust, was associated with coughing during the cold and flu season.
Total levels of particulates were not significantly associated with wheeze or cough, suggesting that individual ingredients – not fine particles as a whole – may be harmful.
This study was the first to investigate the health effects of specific airborne components of heating oil and traffic exhaust.
Nickel and vanadium measurements are highest in the winter and vary throughout the city, figuring more prominently in neighborhoods with older buildings and those closest to ports, according to Lippmann.
Traffic also may be an important source of metal and carbon particles from tailpipe emissions, brake and tire abrasions, and roadway dust.
Though the New York City study looked at the long-term effects on children’s health, many other studies have documented the short-term risks in adults.
Bell and a team of researchers looked at respiratory and cardiovascular hospital admissions of patients 65 years or older associated with same-day exposure to airborne metal components of fine particulate matter in 106 U.S. counties.
Counties with higher nickel, vanadium and elemental carbon were found to have higher risk of hospitalizations associated with short-term particulate exposures, according to the study, published in March in the American Journal of Respiratory and Critical Care Medicine.
In another study, nickel concentrations and cardiovascular deaths in New York City varied widely from neighborhood to neighborhood and were also higher in the winter due to the combustion of residual heating oil. On average, nickel was 9.5 times higher than the average for 60 other U.S. cities, according to the research by Lippmann and colleagues, published this year in the Journal of Exposure Science and Environmental Epidemiology.
Researchers are not sure why certain components of fine particulate matter are more dangerous than others. “It’s a pretty open question right now,” said Miller.
Miller and others suspect the tiny particles, which can settle deep in the lungs, trigger an inflammatory response by the immune system.
“Mid-range atomic metals (such as nickel and vanadium) may be more reactive than other particles,” said Lippmann.