http://scienceline.org/2017/11/clean-chemical-bp-oil-spill-tied-health-problems/
Clean-up chemical at the BP Oil Spill tied to health problems
Scientists link a chemical frequently used to disperse spilled oil to
wheezing, rashes and burning eyes in the recovery workers following the
country's largest-ever spill.
By Will Sullivan | Posted November 8, 2017
Posted in: Environment, Featured
Tags: Corexit, environmental health, Gulf oil spill, NIH
The National Oceanic and Atmospheric Administration responds to about
100 oil spills each year. In each aftermath, the agency studies the
effectiveness of various cleanup methods with hopes of limiting the
impact of future spills on the environment and human health.
One such method is spraying the oil with the chemical Corexit, which
breaks up large clumps of oil into smaller pieces, allowing wind and
waves to more easily sweep it away. But Corexit has been linked to
fast-developing symptoms in the 2010 Gulf of Mexico oil spill’s
30,000-person cleanup crew. These symptoms include wheezing, rashes and
burning eyes, according to a recent study published in Environmental
Health Perspectives in July.
It’s the first study to look at the effects of Corexit on the BP oil
spill cleanup crew.
“Finding that there were acute symptoms suggests to us that we have an
obligation to continue to pursue the question” of whether Corexit might
have long-term health effects, says Dale Sandler, a National Institute
of Health epidemiologist and the study’s principal investigator. She
says the chemical might cause chronic illnesses such as asthma, lung
disease and heart disease. After the April 2010 explosion that killed 11
people, the Deepwater Horizon rig spewed more than 200 million gallons
of crude oil into the ocean. Tens of thousands of workers participated
in the spill’s cleanup, a process expedited by the U.S. Coast Guard’s
application of Corexit.
While some of the chemical components of dispersants are toxic, EPA
testing determined that Corexit was less toxic than a number of other
potential dispersants, Sandler explains. The chemical had been used in
past cleanups, but in smaller quantities and for smaller spills.
One to three years after the BP spill, Sandler and other researchers
surveyed workers exposed to Corexit, asking about current symptoms as
well as any experienced during the cleanup. Even after accounting for
the anticipated health effects of crude oil exposure, the researchers
still found higher rates of symptoms in those exposed to Corexit than
would be expected if the oil dispersant weren’t harmful.
Survey data is inherently subjective, and Sandler cautions that some of
the questions require participants to recall symptoms from up to three
years ago. While the researchers did weed out some unreliable reporters,
it’s likely that the survey data has some inaccuracies. To gather better
data, Sandler says, future studies will use more reliable methods such
as blood tests and clinical diagnoses.
The fact that workers exposed to Corexit got sick is not surprising,
says Samantha Joye of the University of Georgia over email. Joye has
studied the Deepwater Horizon spill extensively and was not involved in
Sandler’s study. Previous studies have shown Corexit harms both human
cells and animals in a laboratory setting.
This is not to say that the use of Corexit resulted in more health
problems than other cleanup tactics might have. Using different
dispersants or burning the oil, which releases carcinogens into the
atmosphere, might have been equally harmful. And while using products
comes with risks, the dispersant does speed up the cleanup process,
limiting air pollution and seabed damage caused by oil. Future research
into the long-term health effects of Corexit will allow researchers to
better weigh the costs and benefits of different cleanup strategies,
Sandler says.
In the meantime, the new results can provide some answers to a community
that has been worrying for years about the effects of the disaster on
their well-being – although questions still remain about the longer-term
health effects of Corexit exposure. “I think the people in the area
deserve to have answers,” Sandler says.
==========================================================================
[link to study: https://ehp.niehs.nih.gov/ehp1677/,
PDF available at:
https://ehp.niehs.nih.gov/wp-content/uploads/2017/09/EHP1677.alt_.pdf]
Environ Health Perspect; DOI:10.1289/EHP1677
Respiratory, Dermal, and Eye Irritation Symptoms Associated with
Corexit™ EC9527A/EC9500A following the Deepwater Horizon Oil Spill:
Findings from the GuLF STUDY
Craig J. McGowan,1 Richard K. Kwok,1 Lawrence S. Engel,1,2 Mark R.
Stenzel,3 Patricia A. Stewart,4 and Dale P. Sandler1
Background:
The large quantities of chemical oil dispersants used in the oil
spill response and cleanup (OSRC) work following the Deepwater Horizon
disaster provide an opportunity to study associations between dispersant
exposure (Corexit™ EC9500A or EC9527A) and human health.
Objectives:
Our objectives were to examine associations between potential
exposure to the dispersants and adverse respiratory, dermal, and eye
irritation symptoms.
Methods:
Using data from detailed Gulf Long-term Follow-up ( GuLF) Study
enrollment interviews, we determined potential exposure to either
dispersant from participant-reported tasks during the OSRC work. Between
27,659 and 29,468 participants provided information on respiratory,
dermal, and eye irritation health. We estimated prevalence ratios (PRs)
to measure associations with symptoms reported during the OSRC work and
at study enrollment, adjusting for potential confounders including
airborne total hydrocarbons exposure, use of cleaning chemicals, and
participant demographics.
Results:
Potential exposure to either of the dispersants was significantly
associated with all health outcomes at the time of the OSRC, with the
strongest association for burning in the nose, throat, or lungs
[adjusted PR (aPR)=1.61 (95% CI: 1.42, 1.82)], tightness in chest
[aPR=1.58 (95% CI: 1.37, 1.81)], and burning eyes [aPR=1.48 (95% CI:
1.35, 1.64). Weaker, but still significant, associations were found
between dispersant exposure and symptoms present at enrollment.
Conclusions:
Potential exposure to Corexit™ EC9527A or EC9500A was associated
with a range of health symptoms at the time of the OSRC, as well as at
the time of study enrollment, 1–3 y after the spill.
https://doi.org/10.1289/EHP1677
[tables are not included in this text, not reproducing well]
Introduction
Background
Over 4.9 million barrels of crude oil was released into the Gulf of
Mexico between the explosion of the Deepwater Horizon rig on 20 April
2010 and the top-capping of the wellhead on 15 July 2010 (United States
Coast Guard 2011). As part of the oil spill response and cleanup (OSRC),
approximately 1.8 million gallons (6.8 million liters) of oil dispersant
was applied both to the sea surface [1.07 million gallons
(4.05 million liters)] and directly into the stream of oil leaving the
wellhead 5,000 feet (1.5 km) underwater [0.77 million gallons
(2.9 million liters)] (United States Coast Guard 2011). Dispersants are
typically used to reduce the interfacial tension between crude oil and
water and facilitate the breakup of oil slicks into small droplets that
are thought to be more easily dispersed by natural processes such as
wind and wave action (Chapman et al. 2007). Two dispersants were used in
the Deepwater Horizon spill response: Corexit™ EC9500A (9500A), which
was applied at both the water surface and the subsurface wellhead, and
Corexit™ EC9527A (9527A), which was applied only at the water surface
(Kujawinski et al. 2011). Both dispersants are composed of propylene
glycol and organic salts including dioctyl sodium sulfosuccinate (DOSS).
Additionally, 9500A contains petroleum distillates, whereas 9527A does
not contain petroleum distillates but does contain 2-butoxyethanol (Wise
and Wise 2011).
Dispersants were applied to the surface either through aerial spraying
or by vessels within 3 nautical miles (5.5 km) of the wellhead area.
Aerial application consisted of both 9527A and 9500A from 22 April until
22 May, after which 9500A was used exclusively. Vessels in the wellhead
area applied 9500A exclusively (BP Gulf Science Data 2016a). Subsurface
application of 9500A was accomplished through a remotely operated
underwater vehicle injecting dispersant directly into the stream of oil
leaving the wellhead (BP Gulf Science Data 2016b). Based on these uses,
the most likely avenues for human exposure among responders are from
dermal exposure and from inhalation of dispersant aerosol droplets.
Previous epidemiologic studies have found adverse health effects
associated with oil spill cleanup work (Aguilera et al. 2010; Laffon et
al. 2016). Effects have included increased lumbar pain, migraine,
dermatitis, eye and throat irritation, and respiratory symptoms. Most
epidemiologic studies have focused on the acute effects of crude oil
exposure during spill cleanup, although Zock et al. (2012) found an
association between participating in cleanup work and self-reported
respiratory symptoms 5 y after the spill response in workers who
responded to the Prestige oil spill in 2002. Although dispersants were
used in some of these previous OSRC operations, no studies looked at
distinguishing effects of exposure to the dispersants.
In contrast, much of the research on dispersants has focused on their
efficacy in dispersing oil (Prince et al. 2013) and on potential adverse
impacts on the environment (Kleindienst et al. 2015). Wise and Wise
(2011) published a review of studies examining the toxicity of various
dispersants, including 9500A and 9527A, in certain model species,
finding that both dispersants exhibited similar acute toxicity to
crustaceans and mollusks and that oral exposure to 9527A adversely
affected intestinal function in rat models.
In response to public concerns regarding the use of dispersants during
the OSRC, the U.S. Environmental Protection Agency (EPA) commissioned a
series of trials testing the acute toxicity of eight oil dispersants in
representative Gulf species, classifying 9500A as either “slightly
toxic” or “practically nontoxic” depending on the species (Hemmer et al.
2010a). Similarly, dispersant–oil mixtures were reported to be no more
toxic to those Gulf species than crude oil alone (Hemmer et al. 2010b).
However, the U.S. EPA did not investigate the effects of exposure to
9527A. Since the spill, additional research has shown that dermal
exposure to 9500A resulted in dermal irritation and sensitization in
mice (Anderson et al. 2011), although a 5-h inhalation exposure to 9500A
did not appear to result in significant adverse pulmonary symptoms in
rats (Roberts et al. 2011). However, these studies of mice and rats did
not include a coexposure of crude oil or other petroleum by-products
that would be expected to be present in the Deepwater Horizon oil spill
environment.
Using in vitro cultures of human bronchial cells, Shi et al. (2013)
showed that exposure to either 9500A or 9527A resulted in a significant
loss of cell viability and that the loss of viability was
dose-dependent. Similarly, Major et al. (2016) found that exposing human
bronchial cells to individual mixtures of 9500A and 9527A with crude oil
induced both cytotoxic and genotoxic effects. Although data on toxicity
of dispersants are limited, there is some evidence of effects caused by
the component ingredients of each dispersant. Human exposure studies
have shown that propylene glycol is a mild irritant when applied
dermally, and animal studies of respiratory effects due to inhalation
exposure are inconclusive (ATSDR 1997). In contrast, 2-butoxyethanol is
considerably more toxic, with acute respiratory effects and eye
irritation observed in both human and animal studies, although minimal
dermal effects have been observed in human studies (ATSDR 1998). The
Material Safety Data Sheet (MSDS) for DOSS lists the chemical as
irritating to the skin and eyes and as a possible respiratory irritant
(Acros Organics 2013). We were unable to find any studies of direct
effects of either 9500A or 9527A on human health.
Given the lack of epidemiologic research into the effects of dispersant
exposure on human health, our study used data from a large cohort of
workers participating in the Deepwater Horizon OSRC to assess two
related objectives. The first objective was to quantify associations of
potential exposure to dispersants with adverse respiratory, eye
irritation, and dermal effects at the time of the OSRC; the second
objective was to quantify associations of potential exposure to
dispersants with adverse respiratory, eye irritation, and dermal effects
in the 30 days before study enrollment, 1–3 years after the OSRC.
Methods
Study Design
Data were from the Gulf Long-term Follow-up Study (GuLF STUDY), a
prospective cohort study of persons involved in the OSRC following the
2010 Deepwater Horizon oil spill (Kwok et al. 2017). Briefly, a total of
32,608 participants completed a telephone interview to enroll in the
study between March 2011 and March 2013. This detailed interview
collected information on particulars of the participant’s OSRC work, if
any, in addition to demographic factors, lifestyle information, and
medical history/symptoms both at the time of the OSRC and at the time of
the interview. The interview for Vietnamese-speaking participants was
abbreviated and did not collect information that could be used to assess
potential dispersant exposure; therefore, those participants (n=999)
were excluded from this analysis. Additionally, we excluded any
remaining participants with missing data on the exposure of interest, on
the outcomes of interest, or on covariates, leaving study populations of
28,636 for analyses of respiratory outcomes, 27,659 for dermal outcomes,
and 29,468 for eye irritation outcomes. The study was approved by the
Institutional Review Board of the National Institute of Environmental
Health Sciences/National Institutes of Health. After receiving
information about the study in the mail, participants provided verbal
consent for the enrollment telephone interview.
Exposure Assessment
Participants were categorized as workers if they worked at least one day
engaged in OSRC activities. Nonworkers received safety training but
never worked on the response. For respiratory and eye irritation
analyses, dispersant exposure for workers was classified as “ever/never”
based on a positive response to any interview question asking about
direct work with dispersants or work on a ship from which dispersants
were applied (see Table S1). Additionally, participants were classified
as exposed if they responded positively to working on any task that
involved dispersant-related equipment, such as pumps, for more than half
of the time. For dermal analyses, dermal dispersant exposure for workers
was classified as “ever/never” based on self-reported skin or clothing
contact with dispersants during the OSRC for breaking up the oil on or
below the surface of the water. Although the questionnaire did not
specifically refer to either Corexit™ 9527A or Corexit™ 9500A by name,
these were the only oil dispersants used during the OSRC, and it is
therefore reasonable to consider reported exposure to dispersants as
reported exposure to either Corexit™ 9527A or Corexit™ 9500A. Office
workers, workers who said no to all dispersant-related questions, and
those who received safety training but did not work on the OSRC were
assumed to be unexposed and were categorized as such for all analyses.
Using publicly available data on dates and locations of use of specific
dispersants in the spill response (BP Gulf Science Data 2016a, 2016b),
we categorized exposed participants as potentially exposed to 9500A only
or as potentially additionally exposed to 9527A. Because 9527A was used
in aerial applications only prior to 22 May 2010, we categorized
participants who reported working on the relevant tasks during that
period as potentially exposed to 9527A. Those who only worked on
spraying dispersant from vessels or pumping dispersant to the wellhead
and those who only reported working with dispersants after 22 May were
classified as potentially exposed to 9500A only.
Additionally, among those classified as exposed in the respiratory and
eye irritation analyses, participants were classified as directly
working with dispersants if they had a positive response to any
questionnaire item related to personally working with dispersants (see
Table S1). Any participant who reported a positive response to a
question about dispersant exposures but did not report this direct
exposure was categorized as indirectly working with dispersants.
Outcome Assessment
Outcomes were based on participant responses to questions on the
enrollment interview about the frequency of symptoms at the time of the
OSRC or at the time of the enrollment interview. Participants reported
the frequency of symptoms on an ordinal scale: “never,” “rarely,”
“sometimes,” “most of the time,” or “all of the time,” and a symptom was
considered present (yes vs. no) if the response was “most of the time”
or “all of the time.” Five distinct respiratory symptoms (cough, wheeze,
tightness in chest, shortness of breath, burning in nose/throat/lungs),
one dermal symptom (≥2 d of eczema, dermatitis, other skin rashes,
sores, or blisters), and two eye irritation symptoms (itchy eyes,
burning eyes) were assessed.
Potential Confounders
We considered a variety of potential confounders. Demographic data
including age, race, gender, and education level, as well as smoking
status, employment status, financial worry, preexisting lung conditions,
potential exposure to equipment decontamination chemicals and
skin/clothing contact with oil or decontamination chemicals were
assessed from responses on the enrollment interview. Residential
proximity to the spill site was categorized based on the proximity of
the county of residence to the Gulf [adjacent to the Gulf Coast,
counties one county inland from the Gulf coast, other Gulf state (AL,
FL, LA, MS, TX) counties, or non–Gulf state counties]. Approximate
maximum daily time-weighted average airborne level of total hydrocarbons
(THC) exposure over all OSRC tasks was estimated using an ordinal job
exposure matrix (Kwok et al. 2017; Stewart et al. in press). Perceived
stress was assessed using Cohen’s Perceived Stress Scale (Cohen et al.
1983).
Statistical Analyses
Owing to the cross-sectional nature of the data and the moderately high
prevalence of the outcomes of interest among the study population (Table
1), we calculated adjusted prevalence ratios (aPRs) as the measure of
effect rather than odds ratios because of ease of interpretation
(Thompson et al. 1998). We fit multivariable log-binomial regression
models to directly estimate the PR for each outcome in the exposed group
compared with the unexposed group. Models were adjusted for a variety of
a priori potential confounders depending on the outcome of interest. All
models were adjusted for age at enrollment (<30, 30–45, >45), race
(white, black, or other), gender, and education level
(>high school degree or not). Models of dermal symptoms were also
adjusted for skin or clothing contact with oil or tar (yes/no) and skin
or clothing contact with equipment decontamination chemicals (yes/no).
Models of both eye irritation and respiratory symptoms were also
adjusted for residential proximity to the spill site, smoking status
(never smoker, former smoker, light current smoker, or heavy current
smoker), potential exposure to equipment decontamination chemicals
(yes/no), and the maximum estimated airborne level of THC exposure (<0.3
ppm, 0.3–0.99 ppm, 1.00–2.99 ppm, ≥3.00 ppm) across all OSRC work.
Models for respiratory symptoms were further adjusted for the presence
of self-reported preexisting lung conditions (yes/no). All models of
symptoms at the time of enrollment were further adjusted for employment
status (employed, unemployed, disabled, retired), financial worry
(yes/no), and Cohen’s Perceived Stress Scale (0–5, 6–10, ≥11) at enrollment.
Because nonconvergence can be an issue with log-binomial regression
owing to the model’s restricted parameter space, we used the weighted
COPY method outlined by Deddens and Petersen (2008) to approximate the
maximum likelihood estimates and related standard errors for any models
that did not initially converge, using 1,000,000 virtual copies of the
data set. All analyses were performed using SAS version 9.3 (SAS
Institute Inc.). We used a significance level of p<0.05 for all analyses.
Sensitivity/Secondary Analyses
Because these data are self-reported, there is a potential for recall
and reporting bias to influence the participant’s reporting of symptoms.
We used self-reported excessive hair loss at the time of the OSRC or in
the 30 d before enrollment to identify participants who may have
over-reported their symptoms because there is no known biological
mechanism that would relate dispersant exposure to excessive hair loss.
All analyses were repeated after restricting the study populations to
those without self-reported excessive hair loss at the time point of
interest (i.e., symptoms during the spill or within 30 d of enrollment)
to help assess any potential impact of reporting bias on the results.
Some nonworkers who completed safety training but were not hired to work
on the OSRC may have had preexisting health conditions or other factors
(such as obesity) that either prevented them from working or made them
less attractive to contractors charged with staffing the cleanup effort.
As such, having them as a part of the comparison group in the analyses
could result in biased estimates in comparison with an analysis
comparing exposed workers with unexposed workers. To help assess any
impact of such a potential healthy-worker selection effect, we repeated
all analyses with nonworkers excluded from the analysis.
Because some participants who worked on land reported working directly
with dispersants, there was concern that participants may have confused
dispersants with chemicals used to clean and decontaminate equipment
because these chemicals were used to “disperse” the oil from the
equipment. Therefore, we conducted a sensitivity analysis excluding any
respondents whose only exposure was reported handling of dispersants on
land who also reported active participation in equipment decontamination
activities. We also conducted sensitivity analyses excluding exposed
workers who reported being exposed outside the known dates of dispersant
use; furthermore, we performed sensitivity analyses assessing potential
confounding resulting from relevant personal protective equipment (PPE)
use during the OSRC (i.e., respirators/facemasks for respiratory
symptoms, rubber gloves or coveralls for dermal symptoms). We also
assessed potential effect measure modification by PPE (i.e., respirator
or face mask) use among respiratory outcomes. More than 97% of those
reporting dermal exposure also reported the use of PPE (i.e., gloves,
protective clothing); therefore, there was insufficient heterogeneity to
investigate potential effect modification of dispersant contact by this
variable (Table 1). In the questionnaire, we did not ascertain whether
PPE was worn during specific tasks, so here, we used overall PPE use as
a proxy.
Among OSRC workers, models of respiratory and eye irritation were
stratified based on three mutually exclusive worker locations—ever
worked on the water in the area of the wellhead, ever worked on the
water but not near the wellhead, or worked only on land—to capture
potential environmental differences between the locations. For example,
workers near the wellhead area would likely have been exposed to
increased particulate matter from the flaring of oil/gas by two vessels
in the wellhead area. For models of symptoms within 30 d of enrollment,
participants were also stratified by the reported presence/absence of
the symptom of interest at the time of the spill in order to investigate
persistence across time points.
Given that those exposed to dispersants largely worked in areas where
they might have also had exposure to THC, we investigated potential
effect modification of the dispersant by the estimated maximum airborne
level of THC (<0.3 ppm, 0.3–0.99 ppm, 1.0–2.99 ppm, and ≥3.0 ppm) over
all OSRC jobs. We also investigated potential effect modification by
exposure to decontamination chemicals. Because 97% of those reporting
skin/clothing contact with dispersants also reported skin/clothing
contact with oil/tar (Table 1), there was insufficient heterogeneity to
investigate whether oil/tar contact modified the effect of dispersant
contact.
Results
Table 1 shows the baseline characteristics of participants in each
analytic study population. Approximately 7.6% of participants included
in the respiratory symptom and eye irritation analyses were considered
exposed to dispersants. Among those included in the analysis of dermal
symptoms, 3.8% had direct skin or clothing contact with dispersants.
The study population was overwhelmingly male; approximately 80% of the
unexposed were men as were ∼90% of the exposed. Those exposed to
dispersants were more likely to be nonwhite, less likely to have any
education beyond high school, and more likely to be <45 y old compared
with those who were unexposed. For the respiratory and eye irritation
analyses, those exposed were more likely to be current smokers (39% vs.
29% for the unexposed) and live in Gulf Coast counties. Given where
dispersants were used during the OSRC, it is unsurprising that those
exposed to dispersants were more likely to have also been exposed to
levels of airborne THC >3.0 ppm (ppm) (53% vs. 7%) and to have worked
with equipment decontamination chemicals (74% vs. 19%). Among those
included in the respiratory analyses, there was no difference in the
prevalence of preexisting lung conditions between the exposed and
unexposed groups. For the dermal analyses, those exposed to dispersants
were substantially more likely to have also come into contact with oil
or tar (97% vs. 31% for the unexposed group) as well as more likely to
have come into contact with equipment decontamination chemicals (60% vs.
5%).
Table 2 presents the prevalence of each symptom reported at the time of
the OSRC along with aPRs. The prevalence of each respiratory symptom
reported at the time of the OSRC (cough, wheeze, shortness of breath,
tightness in the chest, and burning in the nose, throat, or lungs) was
significantly higher in the exposed group than in the unexposed group,
with aPRs ranging from 1.36 [95% confidence interval (CI): 1.23, 1.52]
for wheeze to 1.61 (95% CI: 1.42, 1.83) for burning in the nose, throat,
or lungs. Similarly, the adjusted prevalences at the time of the OSRC
for burning in the eyes and for itching in the eyes, as well as the
adjusted prevalence for ≥2 d of itching or dermatitis, were
significantly higher in the exposed group than in the unexposed group.
Direct exposure to dispersants was more strongly associated with each
respiratory and eye irritation outcome at the time of the OSRC than was
indirect exposure, with nonoverlapping confidence intervals for
shortness of breath (Table 3).
For most symptoms at the time of the OSRC, aPRs were higher for possible
exposure to 9527A than for exposure to only 9500A, although the aPRs
were not markedly different except for tightness in the chest [aPR=1.79
(95% CI: 1.45, 2.21) vs. aPR=1.33 (95% CI: 1.10, 1.63), respectively]
and burning in the nose, throat, or lungs [aPR=1.82 (95% CI: 1.52, 2.19)
vs. aPR=1.22 (95% CI: 1.01, 1.47) respectively], and only the latter
symptom had nonoverlapping confidence intervals (see Table S2).
There was little difference in the associations between symptoms and
dispersant use in analyses stratified by work location, and the
confidence intervals overlapped, although aPRs tended to be higher among
those who worked on the water away from the wellhead than among those
who did not work on the water and those who worked near the wellhead
(see Table S3). Exclusion of participants reporting hair loss (n=578,
n=612, and n=617 for respiratory, eye, and dermal symptoms,
respectively) did not materially change any of the PR estimates or
confidence intervals, although there was a nonsignificant positive
association between self-reported hair loss and dispersant exposure
[aPR=1.24 (95% CI: 0.95, 1.61)]. Similarly, excluding participants whose
only dispersant exposure was on land and who also worked with cleaning
chemicals did not affect the results, indicating that any potential
misclassification resulting from confusing cleaning chemicals with
dispersants was minor. Exclusion of nonworkers and exclusion of
participants with invalid self-reported dates of dispersant use also had
negligible effects on the results.
Stratification by the estimated maximum level of THC exposure over all
OSRC jobs did not reveal any meaningful differences in the associations
between dispersant exposure and any of the respiratory and eye
irritation symptoms at the time of the spill (see Table S4). Reported
PPE use at any time during the OSRC did not confound the association
between dispersant exposure and any of the respiratory or dermal
symptoms at the time of the spill, and there was no significant evidence
of effect measure modification among any of the respiratory symptoms.
For each symptom, the aPR was lower for symptoms present at the time of
study enrollment than for symptoms present at the time of the OSRC
(Table 4). However, dispersant exposure remained significantly
associated with the prevalence of symptoms at the time of study
enrollment, with the exception of cough and skin irritation.
Among participants who reported the presence of a given symptom at the
time of the OSRC, dispersant use remained significantly associated only
with burning eyes at the time of study enrollment. However, among those
participants who did not report a given symptom at the time of the OSRC,
dispersant use was significantly associated with all outcomes except
cough and itching eyes at the time of study enrollment (see Table S5).
Exposure to dispersants was associated with a decreased likelihood of
reported skin irritation within 30 d of enrollment among those who did
not report skin irritation at the time of the spill.
Discussion
This study is the first to evaluate associations between potential
exposure to dispersants, specifically Corexit™ EC9527A or EC9500A, and
respiratory, eye irritation, and dermal symptoms both during the OSRC
and at study enrollment 1–3 y later. OSRC workers with potential
exposure to either Corexit™ product were more likely to have reported
adverse symptoms at the time of the spill. Previous studies have shown
an association between exposure to crude oil and adverse effects among
spill responders (Aguilera et al. 2010; Laffon et al. 2016), but no
previous spill involved this level of dispersant use or resulted in an
investigation of potential associations between dispersant use and
adverse health effects. In vitro results suggested that 9527A and 9500A
may have adverse effects on human lung tissue (Major et al. 2016; Shi et
al. 2013). Our results provide epidemiological evidence to suggest that
exposure to 9527A or 9500A may be associated with adverse health
effects, even after taking into account exposure to the crude oil.
Based on the known irritant properties of chemicals in the dispersants,
we hypothesized that there might be acute effects at the time of the
cleanup, but we did not expect there to be longer-term effects at the
time of enrollment. Although we observed associations between dispersant
use and symptoms at both time points, among participants with a given
symptom at the time of the OSRC, only increased prevalence of burning
eyes at enrollment remained significantly associated with dispersant
exposure, consistent with a lack of persistent effects of the
dispersants. The significant associations between exposure and symptoms
at the time of enrollment among those who did not have symptoms at the
time of the OSRC were unexpected and are difficult to explain. Although
it is possible that these associations are measuring some latent effect
of exposure to the dispersants, another possibility is that some of
these symptoms may have been present at the time of the OSRC but were
not intense enough for the study participants to recall 1–3 y later. The
inverse association between skin/clothing contact with dispersant during
the OSRC and skin irritation reported at the time of enrollment was also
unexpected and is difficult to explain. Many media reports at the time
of the study linked skin lesions with work or recreational activities
involving contact with water from the Gulf of Mexico (Marsa 2016; Landau
2010). We were unable to account for current recreational contact with
the water in this analysis.
As would be expected, direct work with dispersants was more strongly
associated with the respiratory and eye irritation outcomes than
indirect exposure through working in an area where dispersants were
used. Even so, for most symptoms, indirect exposure was significantly
associated with the symptom, indicating that these likely lower
exposures may also be important. Stratification by airborne level of THC
exposure showed no evidence for effect modification by THC on the
associations between dispersant exposure and either respiratory or eye
irritation symptoms.
The exposure measures used in this analysis were based on self-reported
responses to questions about work locations and dispersant-related tasks
and do not allow exploration of exposure–response relationships. A
quantitative job exposure matrix for Corexit™ exposure that takes into
account the chemical and physical properties of the chemicals and
external information on patterns of use may allow evaluation of
exposure–response relationships in the future.
The GuLF STUDY is the largest prospective study of OSRC workers to date,
and it provides an excellent opportunity to investigate less-common
spill-related exposures and health outcomes (Kwok et al. 2017). The
detailed questionnaire provided the opportunity to assess previously
understudied health effects associated with dispersants while also
taking into account a wide variety of potentially confounding factors.
However, our approach relied almost entirely on self-reported data,
which provides several opportunities for bias. When possible, these
potential sources of bias were investigated using a variety of
sensitivity analyses. One potential concern is the over-reporting of
symptoms. We addressed this concern by investigating the relationship
between each exposure metric and self-reported unusual amount of hair
loss at the time of the spill, which does not have any known biological
relationship to exposure to either 9527A or 9500A. The positive
association between dispersant exposure and self-reported excessive hair
loss, although not statistically significant, suggests the possibility
of bias due to over-reporting. However, excluding participants who
reported excessive hair loss did not meaningfully change the results,
suggesting that over-reporting does not explain our findings. Similarly,
exclusion of nonworkers did not result in a meaningful difference in any
of the results, indicating no appreciable effect on the overall
associations resulting from nonworkers potentially having preexisting
worse health than workers (i.e., a healthy worker selection effect).
Associations between dispersant exposure and each outcome were somewhat
stronger among workers who spent time on the water away from the
wellhead than among workers who worked only on land or those workers who
worked near the wellhead. However, associations at all work locations
remained significant, providing evidence that the overall associations
were not being driven by unmeasured characteristics of a particular work
location.
Misclassification of exposure is another potential problem because of
the reliance on self-reported information about the work performed. For
example, there was some evidence in open-ended responses in the
questionnaire that some participants were confused by the term
“dispersant” when responding to questions about decontamination tasks.
We attempted to address this issue by excluding participants who
reported only a land-based exposure and also reported working on
equipment decontamination. The results of that analysis are
qualitatively similar to the overall results, indicating that this
potential misclassification was unlikely to have played an appreciable
role in our results.
It would be expected that the proper use of PPE would help reduce
received exposure and any potential adverse effects of this exposure.
The MSDSs for both dispersants recommend the use of gloves and standard
protective clothing, as well as the use of respirators when
concentrations exceed recommended limits (NALCO 2012a, 2012b).
Measurements taken by BP and by the National Institute for Occupational
Safety and Health (NIOSH) during the OSRC indicate that it is unlikely
that airborne concentrations of either 2-butoxyethanol or propylene
glycol exceeded recommended limits (BP Gulf Science Data 2016c; NIOSH
2010). No measurements were available for airborne concentrations of
DOSS, nor were any dermal exposure measurements during the OSRC
available. Although we had no way to ascertain if PPE was used
specifically during dispersant-related tasks, a sensitivity analysis
among participants who reported PPE use during the OSRC indicated no
confounding of the main association by reported PPE use, nor any effect
measure modification among respiratory outcomes.
Although our results suggest an association between exposure to 9527A,
9500A, or both and adverse acute symptoms, we were not able to
completely distinguish these exposures. Participants who were
potentially exposed to 9527A, as identified by date and method of use,
reported slightly higher prevalence of most symptoms than those who
would have been exposed to only 9500A. Although this outcome could have
been caused by the presence of more acutely toxic agents in 9527A, a
substantially larger quantity of dispersants was applied during the
early period of the OSRC, when both dispersants were being used, than in
the later stages of the OSRC, when only 9500A was used (BP Gulf Science
Data 2016a, 2016b).
Conclusion
Our findings suggest associations between exposure to dispersants,
specifically Corexit™ EC9527A or Corexit™ EC9500A, and adverse acute
health effects at the time of the OSRC as well as with symptoms that
were present at the time of study enrollment 1–3 y later.
Acknowledgements
The authors thank A. Hodges, J. McGrath, and the rest of the staff at
Social and Scientific Systems for data collection and management. We
also thank the GuLF STUDY cohort members.
This study was funded by the National Institutes of Health (NIH) Common
Fund and the Intramural Program of the National Institute of
Environmental Health Sciences/NIH (ZO1 ES 102945).
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