Coping with oil spills: oil exposure and anxiety among residents of Gulf Coast states after the Deepwater Horizon Oil Spill

This is an important paper to show that reliefe activitis may have a beneficial effect on mental status of people affected by a disaster.
Even so, it might be better the author revise the following points.

2. Methods

a It is not clear how the Tobit latent anxiety seviry is used for the study. Did the author re-calculate the level of anxiety among the participants? If so, please describe the modified anxiety levels in Table 2.  Or if the score was used for regression analyses, please describe it.

b Please describe the definition of binge drinking.

c Please include the method of imputation used in Table 1 in the Method section.

d Please describe Wald test used in Table 3 and 4 in the Method section.

3. Results

a Table1. What are the numbers in bracket means.

b Please include average of anxiety score in each group so that the reader can see the trend.

c Table 3 and 4 are not consistent with main manuscript. In manuscript the author use 'beta' as outcome, but the tables show 'difference in anxiety'. Also there is no explanation about what the difference in anxiety means e.g. what score was subtracted by what.

4. Discussion

a Although the author discusse the novelty of the article in 4.2, it is not clear how the article is different from the research of Reference 10.

b As the authors discussed, previous studies sometimes show negative impact of volunteering on mental health. Please add discission about the reason why this discrepancy occurs e.g. differnce in disaster type, characteristics of the residents, etc.

General statement about the manuscript

The research presented in this manuscript describes associations between oil exposure and anxiety after the Deepwater Horizon marine oil spill that occurred in April 2010 and evaluates the following:

1. Effect modification by self-mastery
2. Emotional support
3. Clean-up participation

The authors indicate that the event was historic as it was the largest accidental marine oil spill to date. Their work tested the hypothesis that exposure to oil from the Deepwater Horizon event was associated with anxiety. As described by the authors the main conclusion from this research was oil contact can increase anxiety and this association can be mitigated by clean-up participation. The authors present a conclusion and discussion that support this.

Level of comprehensibility and the style of the paper

Following usual convention, the research was divided systematically into the following:  an introduction, methods, results, and discussion. The manuscript had gradual flow and readability with concepts introduced in a manner that followed a logical progression.

Le vel of importance

The authors present a manuscript with extremely important data, in part because this was such a large and protracted event, impacting public health, which was indicated as part the focus of the research. What makes this spill noteworthy or historic, was the catastrophic loss of human life, unique to this spill. Additionally, this event was a protracted spill that affected many people and their livelihoods. Much research has been done post Deepwater Horizon but as the authors indicate, little on the focus of their particular field of research.  Therefore, this manuscript predicts it will be likely the first to examine associations of anxiety in those that participated in clean-up activities compared to those that didn’t.

This publication has high relevance for academics as well as members of governmental organisations, including oil spill response agencies. It could provide valuable information as to where to direct resources to support emotional health should another event occur.  Proactive techniques may be identified from this research.

Level of completeness

In reading this paper it appeared the introduction was very brief and addressing this brevity forms the basis of this review. This comment is given as there is some background knowledge that further sets the scene for the research and these additional factors if highlighted, could strengthen the introduction. While the paper reads extremely well, this reviewer feels deeper context for readers that are familiar with public health concepts but not oil spill responses could be provided by addressing three sections:

1.Additional commentary about the human cost of this spill, further to what is indicated in the manuscript:

• It is acknowledged that there is background information in the introduction however, some more information on the event itself, such as further defining why this was such a historic event, in no small part because of the human cost to this event, life was lost.  Commentary on this aspect feels critical as the Deepwater Horizon was historic in part because of this uniqueness, because of loss of human life from the explosion on the rig that triggered the spill. Often in oil spill research there is discussion of wildlife, ecosystems, tourism, and livelihoods (as indicated in the manuscript) but this aspect may need reinforcing to describe why this was so historic and so unique.
• A brief statement citing other large spills that have also been termed historic, but for different reasons from the Deepwater Horizon, for example the Exon Valdez.

2.Terminology

While some may argue this is an unnecessary addition this reviewer feels that this would assist readers, that may not understand oil spills or responses, providing context. These small points may strengthen the introduction while not distracting from the core of the research providing a birds-eye view or context including:

• Dispersant is mentioned in the script as a method of remediation, there were other methods of remediation used in this spill response. A definition for the reader describing what dispersant is with a reference, would be useful as there are many different types and a long process of decision making before utilizing it.  A dispersant is also a contaminant, toxic and can contribute to the damage of the ecosystem and there are also human health implications.  As public health is a focus of this paper it may be worth mentioning.
• For readers that are unfamiliar with oil spill terminology, a simple statement converting barrels of oil to gallons would provide the reader with a clear understanding of the massive volume of oil discharged in this event and then provide a basis of understanding should they want to investigate other spills as a comparison of impact through volume spilled.
• While a mention of the type of oil was mentioned a comment about different oils may be useful.  Why?  If it was a light fuel oil such as diesel, depending on weather conditions and other factors it theoretically evaporates easily and be dispersed by the energetic activity of the environment. Dispersed oil (while still toxic, highly volatile and damaging to the environment and animals) is less visible to residents, communities, and the general public, and may disperse before impacting coastlines in the area.  Heavy fuel oil or crude oil in an environment can have an impact on people as it is visually distressing, has a smothering effect on animals and the environment and widely reported in the media.

3.Methods

• Further discussion explaining why particular measurement tools were chosen over others would provide more insight . For example, self-mastery was mentioned as a key indicator tested, it would have been useful for me as a reader to know a little more about this beyond coping ability and further exploration or brief comment of why coping ability promotes resilience?
• Readers may experience some confusion about the terms “directly exposed to oil” and “direct contact” as both were presented. It is unclear if it refers to being exposed from the point of view of hands-on contact with oil through clean-up participation or activities as a volunteer or part of a professional oil spill response agency. Does “exposed” refer to residents seeing oil beached, or “exposed” to oil through loss of livelihood, employment or tourism. Clarification could remove any ambiguity for the reader. If there was “direct contact” was that as part of a professional oil spill response agency, part of an orchestrated clean-up effort as part of the Deepwater Horizon wider response or “exposed” individuals acting alone.  Knowing that could provide context around the anxiety that was experienced.

In summation

While the target audience for this manuscript may be involved in public health, other agencies will be very interested in this research. This is a very thought-provoking manuscript that provides useful but also important ideas and data. This subject is critical for integration into public health commentary in the future. Provision of further context including some terminology and explanation to the points noted in this review may assist future readers to gain full appreciation of the scale and complexity of the Deepwater Horizon event and the effect and anxiety it created within the community and individuals.