Black carbon in homes: New York City's asthma culprit.

Jul 12, 2012

Cornell AG, SN Chillrud, RB Mellins, LM Acosta, RL Miller, JW Quinn, B Yan, A Divjan, OE Olmedo, S Lopez-Pintado, PL Kinney, FP Perera, JS Jacobson, IF Goldstein, AG Rundle and MS Perzanowski. 2012. Domestic airborne black carbon and exhaled nitric oxide in children in NYC. Journal of Exposure Science and Environmental Epidemiology http://dx.doi.org/10.1038/jes.2012.3.

Synopsis by Virginia T. Guidry

Elevated levels of black carbon inside New York City homes are likely to be in neighborhoods where more kids have asthma, a study has found. Proximity to major truck routes and buildings using low-quality fuel oil were related to the black carbon levels inside homes. The results add important information about the respiratory effects of air pollution on children.

Home air quality has a big impact on kids’ health, and the quality of the indoor air depends in part on the quality of the air outdoors. Such is the case with levels of black carbon – a small particulate formed from incomplete burning of fossil fuels and wood.

A study in New York City has found that homes with higher levels of the pollutant inside were more likely to be in neighborhoods with a high percentage of kids with asthma.

Black carbon is a major contributor to airborne pollution known as “fine” particulate matter. The tiny particles are known to have big health impacts on the heart and respiratory system because they can penetrate deeply into the lungs.

This is the first study to connect levels of black carbon in people’s homes with sources nearby. Both proximity to major truck routes and the density of nearby buildings using low quality fuel oil were related to the black carbon levels in homes.

This study also used a new marker of lung inflammation called fractional exhaled nitric oxide (FeNO). Increased FeNO in exhaled air indicates lung damage before it becomes a full-blown health problem. A person with this preliminary inflammation exposed to a strong trigger such as stress, illness or allergens may have an asthma attack.

The researchers compared 240 children from neighborhoods in New York City that were classified as having either low asthma prevalence or high asthma prevalence. Parents reported asthma status in a questionnaire. During an extensive home visit, exhaled FeNO was measured; blood samples were collected to test for allergies; and bed dust was collected to determine the presence of allergens from dust mites, dogs, cats, mice and cockroaches.

Higher black carbon levels at home were associated with a higher percentage of kids with asthma in the surrounding neighborhood.

Among children with no sensitivity to common allergens, higher black carbon levels were also associated with higher FeNO. For children with sensitivity to allergens, dust mite allergens in bed dust – but not black carbon – were associated with elevated FeNo.

The study participants were from a health insurance database for middle-income families, so findings are less likely to result from differences in income, a common factor in urban asthma studies. One limitation is that black carbon levels were collected after FeNO measurements, though the researchers provide good evidence that these measurements accurately represent home exposures.

The results support a need for further air quality regulations intended to protect public health, such as those recently proposed by the U.S. Environmental Protection Agency to limit soot.

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