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Workers who responded to the Deepwater Horizon oil spill in 2010 were more likely to report incident asthma within a few years, a cohort study found.

Those oil spill response and cleanup workers were 60% more likely to report developing asthma in the 1-3 years after the spill compared with non-workers who had been trained but not hired (RR 1.60, 95% CI 1.38-1.85), according to findings in .

In particular, asthma was linked to increased exposure to airborne crude oil chemicals, namely total hydrocarbons (THC), and volatile organic compounds in the benzene, toluene, ethylbenzene, o-, m-, and p-xylenes and n-hexane (BTEX-H) group, reported Dale Sandler, PhD, epidemiologist at the NIH National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina, and colleagues.

"This is the first study to ever look at specific chemicals from oil spills and link them to respiratory diseases," Sandler said in a . "If you were an oil spill cleanup worker in the gulf experiencing wheezing or other asthma-like symptoms, it would be good to let your healthcare provider know you worked on the oil spill."

The is considered the largest industrial marine oil spill in history. The spill began in April 2010, and the flow was only declared capped after 87 days and approximately 4.9 million barrels of crude oil were released off the coast of the U.S. in the Gulf of Mexico.

Since then, there have been many for the tens of thousands of workers who directly aided in the cleanup.

THC represents a broad category of volatile components in liquid crude oil. Within THC are BTEX-H chemicals -- previously linked to cancer, lung disease, asthma, and reduced lung function -- which the U.S. classifies as hazardous air pollutants.

In addition to THC and BTEX-H chemicals, spill response workers were also exposed to particulate matter smaller than 2.5 micrometers (PM_2.5) from the burning of oil and natural gas. The risk of asthma with greater PM_2.5 exposure was attenuated upon adjusting for THC, Sandler's group found.

PM_2.5 has been linked to asthma in both general population studies and in occupational studies, but its association with asthma varies based on the composition of the particulate matter, the researchers noted.

Their prospective focused on 19,018 workers (average age 42 years, 66% white, 83% men) without asthma before the spill.

For comparison, a cohort of 5,585 nonworkers (average age 44 years, 64% white, 76% men) also was included in the analysis.

THC and BTEX-H exposures were estimated based on job type and air samples taken throughout the Deepwater Horizon cleanup effort, whereas PM2.5 exposure was based on modeled estimates.

Incidents of asthma were defined as self-reported wheezing or self-reported physician's diagnosis of asthma that occurred 1-3 years following exposure -- a method that did leave room for misclassification bias, Sandler and colleagues acknowledged.

As 87% of identified asthma cases did not have a physician's diagnosis, the incidence of asthma was potentially overestimated.

"Because the GuLF STUDY population is socioeconomically vulnerable, with less than half reporting access to medical care, we included non-doctor confirmed asthma cases to minimize any underreporting of true asthma cases in the population that would be missed due to lack of access to health care," Sandler explained in the press release.

The generalizability of this study may also be limited due to the unique exposure faced by GuLF Study participants.

Finally, study results may have been affected by unmeasured confounding factors.

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