By Paul Whaley
As a society we could do much better at incorporating environmental health science into clinical advice and policy recommendations.
Take formaldehyde: In the early 1980s multiple studies in rats were showing that exposure to formaldehyde increased their chances of developing nasal cancers. However, it took another 20 years of human observational research to pile up, confirming the same health outcome in people, for formaldehyde to begin being restricted.
Bisphenol-A (BPA), the controversial plastic additive, is shaping up as a classic contemporary example of the problem public health practitioners had with formaldehyde. In this case, there are around 1,000 studies of its potential health effects – but there is still only political wrangling instead of a clear decision on whether or not it is safe.
Environmental health experts know there is a substantial body of evidence connecting environmental chemicals with a range of diseases including cancer, neurodegenerative disorders, autism, diabetes and so forth. However, the cases of formaldehyde and BPA show there are significant obstacles between the acquisition of environmental health knowledge and society then acting to protect public health. In the case of formaldehyde alone, this arguably meant 20 years of unnecessary nasal cancers in people.
The slow speed at which environmental health research shapes policy and clinical action may be due in part to differences between environmental-health and clinical research, and several groups are working to address this gap.
Tracey Woodruff, MPH, Director of the Program for Reproductive Health at the University of California San Francisco (UCSF), is well aware of the issue. As a public health practitioner concerned with reproductive health, she explains that when she first started becoming aware of increasing rates of endometriosis and infertility in her patients, at the time not only was she herself unable to explain why this was the case, there was nothing to which she could refer which would help her understand the origins of the changes she was seeing.
Woodruff is now coordinating a committee of medical and public health practitioners which believe a major part of the problem has to do with the fundamental differences between how environmental health and clinical research is conducted and presented. The committee believes it is a lack of understanding of the merits of environmental health data which is leading to a mistaken sense among clinicians that environmental health evidence is irrelevant to clinical practice, when in fact the data is just different.
Chief among the differences is the use of the randomised controlled trial (RCT), considered the “gold standard” of evidence for medical diagnostic testing. While it is a staple of clinical research, and forms the content of almost all studies published in the mainstream medical literature, the RCT is almost completely absent from the environmental health evidence base. There is one major reason for this: it is unethical to expose humans for research purposes to a substance suspected of causing harm, so the RCT is almost always off-limits for environmental health researchers. This limitation is also accepted in medicine, in the prohibition of testing drugs on pregnant women.
In place of RCTs, human observational studies assume greater comparative importance in understanding how exposure to environmental chemicals may affect health. The importance of observational evidence should not be understated, with many examples of it being strong enough to justify intervention, as shown for example in identifying the toxicological hazard posed by diethylstilbestrol (DES). In this case, alert clinicians collected enough data about prenatal exposure to DES for it to be connected to increased rates of rare reproductive cancers in women.
Besides human observational studies, the other important information available to environmental health researchers are in vivo animal tests and in vitro experiments. Although used widely in the pharmaceutical industry to decide if a drug is worth testing on – or indeed safe for – humans, the discovery of toxic effects in animals does not seem to carry the same significance when it comes to determining harm from man-made chemicals.
The concern is this almost exclusive attention given to RCTs means the other types of evidence are being discarded and perceived as irrelevant to medical practice. Because of this perception, environmental health as a formal subject is not part of medical education. As a result, doctors are either uncomfortable handling the issues – for example, most paediatricians in a study in the US state of Georgia were not comfortable taking an environmental history, even though more than half reported having a patient seriously affected by an environmental exposure – or likely to be dismissive of their importance. This makes non-clinical studies further unlikely to be published in the mainstream medical journals, meaning the evidence is never presented to doctors, perpetuating the problem.
Resolving this situation is difficult. If the science is not seen as relevant to health by the medical community, then there is little point in trying to force it into education or clinical practice; anyone who has spoken to medical lecturers about additions to curricula will know how hard it is to add content to a trainee doctor’s education. Nor do clinicians want to have more to do in the limited amount of patient contact time.
Efforts to make environmental-health research accessible
So what to do? According to Mark Miller MD, Director of the UCSF Pediatric Environmental Health Specialty Unit and a member of Woodruff’s working group, the first step is making a science sometimes perceived as “whacky” accessible to clinicians: “The key is sorting out the materials so they are acceptable to the clinical community – they have to meet the standards of that community, be written in a language the community understands, which stands up to the concerns of clinicians.”
To address these issues, Woodruff’s committee is looking at adapting to environmental health science the GRADE approach to evaluating clinical interventions. Increasingly adopted worldwide and endorsed by, among others, the Cochrane Collaboration, the British Medical Journal and the American College of Physicians, GRADE uses a fixed methodology to make recommendations about clinical interventions.
If a similar system could be developed for environmental health, particularly with a trusted and transparent methodology, Woodruff believes that a significant forward step in incorporating environmental health into medical practice would have been taken. If environmental health science can be gathered and presented using a transparent methodology, statements of best knowledge and related clinical and policy guidance materials would become an unimpeachable source of information, in much the way International Agency for Research on Cancer Monographs and Cochrane reviews are now for clinical interventions.
Tentative steps toward building this sort of system are being taken in the UK. Mark Starr, the principal software architect behind the Cochrane Database of Systematic Reviews, which later evolved into the Cochrane Library, is developing a system called “Sustainability for Health: an Evidence Base for Action” (SHEBA), designed to assemble environmental health knowledge into one place, and then push this through a Cochrane-style review process to determine the most important and effective practical and policy-based interventions for minimising harm to health from environmental causes. (I am personally involved in this project. Although the website is visible it is still under development – anyone interested in more information should feel encouraged to contact me.)
Miller describes the moving of clinicians attention towards “looking at the causes of problems and getting stuck into the public health issues which lead to them having a patient on the table in the first place” as a key objective for reducing the harm done to health by the environment. Making environmental health science more relevant to the work of clinicians and public health policy-makers seems to be a vital part of that process.
Paul Whaley is editor of the website and monthly e-publication Health & Environment, which emphasises to medical practitioners and public health policy-makers the importance of the environment as a determinant of public health. (See some of their materials for clinicians here.) He also serves as curator of the Environmental Chemicals Stream for Sustainability for Health: an Evidence Base for Action (SHEBA) and is the communications manager for the Cancer Prevention and Education Society. He can be reached at firstname.lastname@example.org.