Deepwater Horizon oil spill cleanup workers experience increased risk for asthma

Key takeaways:

• Workers involved in cleaning up the Deepwater Horizon oil spill were 60% more likely than those who did not work on the cleanup to be diagnosed with asthma or experience asthma symptoms between 1 and 3 years after the spill.
• Workers involved in operating, maintaining or refueling the heavy cleanup equipment had the highest incidence of asthma.
• Less than half of the participants in the study reported access to medical care, suggesting that true asthma cases may be underreported in the population.

Workers who participated in the cleanup of the Deepwater Horizon oil spill experienced an increased risk for asthma due to exposure to total hydrocarbons and PM_2.5 air pollutants, according to a study published in Environment International.

“At the time of the disaster, little was known about short- and long-term health effects related to oil spill response and cleanup work exposures,” Dale P. Sandler, PhD, chief of the National Institute of Environmental Health Sciences (NIEHS) Epidemiology Branch, told Healio.

“Furthermore, the magnitude of the disaster and number of those potentially exposed — tens of thousands of cleanup workers — was unprecedented, prompting health and safety concerns for those involved,” Sandler said.

The Gulf Long-term Follow-up (GuLF) Study Program was designed to study the health of individuals who helped with the oil spill response and cleanup following the Deepwater Horizon spill.

Led by the NIEHS and funded by its intramural program, it is the first study to look at specific chemicals from oil spills and link them to respiratory diseases, according to the researchers.

“The NIEHS mission is to discover how the environment affects people in order to promote healthier lives,” Sandler said.

Pollutant and participant profiles

In 2010, the Deepwater Horizon oil drilling platform spilled 4.9 million barrels of crude oil into the Gulf of Mexico. During the cleanup, workers were exposed to volatile total hydrocarbons (THC) including benzene, toluene, ethylbenzene, o-xylenes, m-xylenes, p-xylenes and n-hexane (BTEX-H).

The U.S. Clean Air Act has classified BTEX-H chemicals, which have been linked with adverse health outcomes such as cancer and lung disease, as hazardous air pollutants.

Workers also were exposed to PM2.5 from burning/flaring, which the EPA has classified as an air pollutant and which has been established as a risk factor for asthma as well.

“The current research focused on asthma,” Sandler said. “Although previous studies did not consider the potential longer-term risks associated with individual oil spill chemicals, or asthma, per se, there is evidence from previous oil spills that exposures during spills can lead to respiratory health symptoms.”

The researchers examined data from 19,018 workers (mean age, 42 years; 66% white; 93% non-Hispanic; 83% male) who spent at least 1 day participating in the cleanup and 5,585 people who were trained but who did not participate in the cleanup. Of the workers, 53% had never smoked, with an average of 16 pack-years (standard deviation, 18) among those who had. Also, 13% had worked on other oil spill cleanups, and 16% had previous oil industry experience.

Prior to the spill, none of the participants in either cohorts had been diagnosed with asthma based on a physician diagnosis or self-reported wheeze.

Cleanup jobs from highest to lowest exposure included response, operations, cleanup on water, decontamination, cleanup on land, and support. Examples include administrative support, environmental water sampling, mopping up crude oil and decontaminating equipment or wildlife.

The results of exposure

Overall, 983 participants had asthma cases that emerged 1 to 3 years after the spill. Noting that the population of the study was socioeconomically vulnerable, with less than half reporting access to medical care, the researchers included nondoctor-confirmed asthma cases to minimize any underreporting due to lack of access to health care.

Workers who participated in cleanup efforts in any capacity experienced a higher risk for incident asthma (adjusted RR = 1.6; 95% CI, 1.38-1.85). Compared with workers in support roles, workers in operations (RR = 4.29; 95% CI, 3.16-5.82) and response (RR = 3.8; 95% CI, 2.42-5.99) roles had the highest risks for asthma.

“We found oil spill cleanup and response workers were 60% percent more likely to develop asthma within 1 to 3 years of the Deepwater Horizon disaster compared with nonworkers,” Sandler said.

Exposures to higher levels of THC, individual BTEX-H chemicals and the BTEX-H chemical mixture were each associated with increased asthma risk, the researchers found.

Specifically, the risk for asthma was higher among workers in the highest quintile of THC exposure compared with the lowest quintile of exposure (RR = 2.95; 95% CI, 2.33-3.74).

Similarly, workers in the highest quintiles for exposure to each BTEX-H chemical had increased risks for asthma in an exposure-dependent manner (P < .0001) compared with the lowest quintiles in fully adjusted models. The researchers additionally found an estimated 45% increase in asthma risk per quartile associated with the overall BTEX-H mixture (RR per quartile = 1.45; 95% CI, 1.35-1.55).

“Associations with BTEX-H chemicals were particularly interesting since no prior study has assessed asthma-related health risks related to this chemical mixture among oil spill cleanup workers before,” Sandler said.

However, there were no substantive differences for associations between asthma and THC or BTEX-H in secondary analyses that excluded workers who were exposed to burning or flaring oil or gas exposures.

In an industrial hygiene review, workers with the highest potential exposure to burning or flaring oil or gas had an elevated risk (RR = 1.67; 95% CI, 1.16-2.4) compared with unexposed workers, although this risk was attenuated after adjustments for THC (RR = 1.37; 95% CI, 0.94-1.96).

The more that workers were exposed to these crude oil chemicals, the more likely they were to have asthma symptoms, the researchers wrote, as exposure levels varied depending on the job and how long it was performed.

Further, asthma risks increased with maximum 12-hour PM_2.5 exposure (RR = 1.37; 95% CI, 1.12-1.68) before THC adjustment, with attenuation to 1.16 (95% CI, 0.95-1.42) after adjustment.

When asthma was only defined based on a physician’s diagnosis, the associations between asthma and oil spill exposures largely attenuated and exposure responses no longer were apparent for any associations.

According to the researchers, these associations may be due to wheeze symptoms instead of asthma, or they may indicate differences between workers who did and did not have access to medical care, suggesting that clinical asthma was undercounted.

Still, the researchers concluded that THC, individual BTEX-H chemicals and the BTEX-H mixture each had an association with increased risk for asthma in an exposure-dependent manner for workers involved in the Deepwater Horizon cleanup.

The need for care

With 5% of cleanup workers reporting asthma and asthma symptoms compared with 3% of nonworkers, the researchers noted that workers who are experiencing wheezing or other asthma-like symptoms should let their health care providers know that they had worked on the oil spill.

“During the active cleanup period, workers could take advantage of clinics set up to address short-term health concerns. No formal program of health care specifically devoted to clean-up workers is available,” Sandler said.

The GuLF Study team worked with local providers to develop a list of local referral resources. Also, participants enrolled in the study receive newsletters updating them on current research findings. The study’s website offers a current list of study findings as well.

The GuLF Study will continue to follow its nearly 33,000 participants to monitor potential health outcomes and answer important public health questions, the researchers wrote.

These findings also will inform best practices during future cleanups.

“We recommend that cleanup workers coordinate with on-site industrial hygienists to follow safety precautions and consider proper use of available recommended personal protective equipment to best protect their health,” Sandler said.

For more information:

Dale P. Sandler, PhD, can be reached at sandler@niehs.nih.gov.

References:

• GuLF Study publications. https://gulfstudy.nih.gov/en/publications.html. Updated April 7, 2022. Accessed Aug. 19, 2022.
• Oil spill cleanup workers more likely to have asthma symptoms. https://www.nih.gov/news-events/news-releases/oil-spill-cleanup-workers-more-likely-have-asthma-symptoms. Published Aug. 17, 2022. Accessed Aug. 18, 2022.