Cane Burning Study is Flawed and Misleading

HC&S Puʻunēnē Mill. Photo by Wendy Osher.

By HC&S General Manager Rick Volner

Scientific research on public health issues can be valuable in setting policy and educating the public on the health impacts of certain behaviors and practices. Unfortunately, no such benefits will be delivered by the recently published study association between sugar cane burning and acute respiratory illness on the island of Maui featured in an Oct. 13 Civil Beat article (“Study: Large Cane Burns Linked to Acute Respiratory Distress”) and an Oct. 28 Maui Now article (“Cane Burning Study: Health Officials… Take Action“).

Indeed, the publication of fatally flawed research, like this study, undermines effective policy making and only creates confusion in the community on key issues.

Evaluations conducted by independent experts, as well as our own review, have exposed significant flaws in the study’s methodology and analysis. Moreover, the authors’ conclusions are undermined by the study’s own data.

Flawed Methodology
A significant flaw in the study is that instead of using medical diagnoses of illness or disease, the authors rely upon prescription fills at selected area pharmacies as an indicator that the person filling the prescription experienced respiratory distress as a result of cane burning. It is questionable whether prescription fills are a reliable indicator of symptoms of an associated illness. More importantly, the prescriptions recognized by the study are non-specific to respiratory disorders. Some of the medications are used to treat a wide range of ailments, including conjunctivitis (“pinkeye”), arthritis, intestinal disorders, lupus, and even cancer, among others. A similar problem exists with the hospital emergency department data, in that “headache” and conjunctivitis were considered symptoms of respiratory distress.

Exposed or Not?
An essential element of a study such as this is the ability to clearly differentiate between exposed and unexposed populations. In this study, “exposure” to cane smoke was assumed to have occurred simply based on subjects’ home addresses, so-called “average” wind directions, and a crude estimation of “downwind” populations. In reality, the authors have no way of knowing who was exposed to cane smoke and who was not – making those subsequent evaluations of respiratory distress meaningless.

Study’s Findings
Based on this flawed methodology, the study authors conclude that there was a higher incidence of respiratory distress in smoke-exposed regions when more acres were burned. Yet the study states “there was a significantly higher rate of respiratory illness on the days when cane was not burned” than on the days when cane was burned, and that the predicted association between cane burning and respiratory distress “was not supported with either hospital data or pharmacy data.”
The authors then try to explain away the higher rate of respiratory illness reported on days when cane was not burned, a finding that was clearly contrary to their expectations. They do so by assuming that vog must have caused the respiratory problems on non-burn days. Their reasoning? The burn permit does not allow cane to be burned on days when there is vog or rain. The authors therefore conclude that all non-burn days were vog days.

What the authors fail to disclose is that 90 percent of the non-burn days included in the study occurred after the sugarcane harvesting season had already ended when no burning was conducted, regardless of conditions. The report provides no evidence whatsoever that vog was present on any of these off-season, non-burn days, much less causing any respiratory illness. Thus, the attempt to explain away the data’s finding of a higher rate of respiratory illness on non-burn days is not supported by the facts.

Only by excluding from consideration the burns least likely to support their hypothesis, and after-the-fact re-analysis of the data, were the authors able to make a link between cane burning and an increase in prescription fills. Yet, the study still fails to establish that there was any connection between prescription fills and actual exposure to cane smoke by those filling the prescriptions.

Ignoring Relevant Research
The authors incorrectly state that no studies examining health effects of sugarcane burning in Hawaii have previously been conducted. In fact, there are several well-designed and widely available epidemiological studies conducted in Hawaii (including on Maui) by the Hawaii Department of Health, University of Hawaii School of Public Health, National Institute of Occupational Safety and Health, and Centers for Disease Control.

These epidemiological studies did not identify any significant association between sugarcane burning in Hawaii and the occurrence of a wide variety of health effects, including asthma, findings which are at odds with the unsupported conclusions of the study reported on in the article.

The study not only fails to advance understanding of the issue in question, but also works to compound misunderstanding about cane burning. Given the contradictory conclusions, failure to follow generally accepted scientific methodology and misleading use of data, this study should not be used to sway public opinion or to make public policy decisions.