Research digest #2 (Oct 2013). Recent peer-reviewed research into chemical toxicity (non-human), risk assessment and risk managementOctober 19, 2013 at 10:59 am | Posted in 5&5 News & Science | Leave a comment
Perinatally Administered Bisphenol A as a Potential Mammary Gland Carcinogen in Rats. These findings suggest that developmental exposure to environmentally relevant levels of BPA during gestation and lactation induces mammary gland neoplasms in the absence of any additional carcinogenic treatment. Thus, BPA may act as a complete mammary gland carcinogen. (Study synopsis here.)
EDCs: negotiating the precautionary principle. LANCET (Diab & Endo): Few scientific issues are more complex or controversial than assessment of the effects of endocrine-disrupting chemicals (EDCs) on human wellbeing. Several scientific disciplines are involved—including toxicology, endocrinology, environmental science, paediatrics, obstetrics and gynaecology, and public health—each with different questions and priorities.
Policy Decisions on Endocrine Disruptors Should Be Based on Science Across Disciplines: A Response to Dietrich et al. “We are writing as scientists and editors of leading peer-reviewed journals that have published important contributions in the study of endocrine disrupting chemicals (EDCs). By signing this editorial, we affirm that regulatory decisions on EDCs should be made based on the best available science and expertise that involves, among others, reproductive biology, endocrinology, medicine, genetics, behavior, developmental biology and toxicology.”
Tags: BPA, chemical risk assessment, chemicals, epidemiology, PFCs, phthalates
The Human Urine Metabolome. Urine has long been a “favored” biofluid among metabolomics researchers. After 7 years’ work, an online database containing the complete set of 2651 confirmed human urine metabolite species, their structures (3079 in total), concentrations, related literature references and links to their known disease associations has now been developed.
Phthalates and the diets of US children and adolescents. Diet contributes to urinary phthalate concentrations in children and adolescents. Further study is needed to examine the implications of di-2-ethylhexylphthalate exposure, especially earlier in life, when more permanent metabolic changes may occur.
Human exposures to bisphenol A: mismatches between data and assumptions. The conflict between reported data and toxicokinetic models has spurred considerable debate, with some suggesting that data from analyses of human blood should be dismissed in their entirety. To the contrary, this review considers evidence that challenges the assumption that humans metabolize BPA rapidly enough to result in undetectable levels in blood, to therefore determine that there is a possibility of harm from current exposure levels.
Prenatal Exposure to Persistent Organochlorines and Childhood Obesity in the U.S. Collaborative Perinatal Project. This study evaluated the association of maternal serum levels of β-hexachlorocyclohexane (β-HCH), p,p´-DDE, dichlorodiphenyltrichloroethane (p,p´-DDT), dieldrin, heptachlor epoxide, HCB, trans-nonachlor, oxychlordane, and PCBs with offspring obesity during childhood. No clear associations with obesity or BMI emerged.
Association between Perfluoroalkyl substances and thyroid stimulating hormone among pregnant women: a cross-sectional study. Results of this study suggest an association between PFOS and TSH in pregnant women that is small and may be of no clinical significance.
Bisphenol A and Human Health: A review of the literature. This review discusses the growing human literature correlating environmental BPA exposure to adverse effects in humans which, along with laboratory studies in many species including primates, it argues provides increasing support that environmental BPA exposure can be harmful to humans, especially in regards to behavioral and other effects in children.
Tags: chemicals, endocrine disrupting chemicals, journal editors, journal endocrinology, science, toxicology journals
Normally a reclusive subject rarely sighted in the media, the intersection between science and chemicals policy has been unusually prominent this summer, with the editors of journals of toxicology, endocrinology and other related fields publishing combative editorials about how endocrine disrupting chemicals should be regulated.
This started on 5 July 2013 when four toxicology journals published an editorial which stuck a somewhat less than conciliatory tone (Dietrich et al. 2013): “Scientifically unfounded precaution drives European Commission’s recommendations on EDC regulation, while defying common sense, well-established science and risk assessment principles.”
On 27 August 2013, a responding commentary was published in Environmental Health (Bergman et al. 2013): “Science and policy on endocrine disrupters must not be mixed: a reply to a “common sense” intervention by toxicology journal editors.” It was accompanied by an editorial by the journal editors (Ozonoff & Grandjean 2013).
Then on 18 September 2013, a second commentary was published in the journal Endocrinology (Gore et al. 2013): “Policy Decisions on EDs Should be based on science across disciplines: A Response to Dietrich et al”, also accompanied by an editorial “riposte to naysayers” (Gore 2013).
According to the commentaries and editorials, Dietrich et al. have a number of questions to answer. Eight of them are as follows.
1. Why Dietrich et al. left the programming function of hormones out of their account of endocrine function, instead narrowly defining it in terms “of keeping an organism’s response within the homeostatic space”. This is a view which sees endocrine disrupters as only those chemicals which take an organism outside of its adaptive range, and disregards experimental information going back 50 years about the role hormone signalling has during specific windows of development.
2. Why if EU regulation is based on an a priori default assumption of no thresholds for regulating endocrine disrupters, as Dietrich et al. claim, there is no legal document presented which substantiates this statement.
3. How it can be that a policy framework developed by the EU Endocrine Disrupters Expert Advisory Group, consisting of 43 experts from 19 EU Member States, NGOs, the industry-funded research association ECETOC, among others, can have proposed a regulatory framework, as Dietrich et al. say, “based on virtually complete ignorance of all well-established and taught principles of toxicology and pharmacology”.
4. How, as implied by their reasoning, changing the default assumption that for regulatory purposes toxicological tests on animals are relevant for anticipating human health risks unless proven otherwise, to a default assumption that animal tests are not relevant to humans unless proven otherwise, is at all workable.
5. How “[t]housands of published studies have revealed health effects of EDCs on wildlife and laboratory animals, and moreover, have shown associations of EDCs with effects in humans” (Gore et al. 2013) yet according to Dietrich et al. that proposed EU legislation on endocrine disruptors is nonetheless driven by “scientifically unfounded precaution”? To put it another way: what evidence does Dietrich et al. think is required for “precaution” to be placed on scientific foundations – or is precautionary policy inevitably unscientific?
6. If precautionary policy is by its nature unscientific, then there is a question as to where Dietrich et al see the division between what constitutes science and what belongs to the realm of societal and democratic choices. Even if the regulation of endocrine disrupters is driven in part by “the emotions that critics of industrial chemicals have raised”, these are societal choices which have led to the Precautionary Principle being enshrined in European Law in the EU Treaty.
To prevent any confusion about exactly what constitutes the Precautionary Principle, it is Principle 15 of the Rio Declaration: “[I]n order to protect the environment, the precautionary approach shall be widely applied by States according to their capability. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation”.
This is a legal concept for addressing scientific uncertainty. Researchers first develop the evidence-base for endocrine disrupting effects of chemicals; the legislature then decides what to do, with the Precautionary Principle being a guiding instrument in that decision-making. The appropriateness of scientists (or anyone else) disputing the application of EU law in terms of how they see evidence for effects confuses the distinction between what the evidence is, what actions might be justified on the basis of that evidence, and the legal instruments by which those decisions are made. (You can disagree with the evidence and the action, but that says nothing at all about the validity of a legal instrument – particularly one designed to help regulators cope with disagreement about the evidence.)
7. There is a question of the value of statements like “well-established and taught principles of toxicology and pharmacology”. It may well be that anticipating the effects of endocrine disruptors requires changes to our understanding of the principles and conduct of toxicological research, but then science changes all the time – in a well-worn example, that Newtonian physics was “well-established and taught” was no objection to Einstein’s theories of relativity.
As Gore et al. put it, “common sense dictates that policies, particularly those in which public health is at stake, should be based on scientific evidence obtained from the world’s leading researchers, and should derive from a more evolved, modern understanding of the science, rather than on older, outdated concepts and data taught in classrooms 20 or more years ago.” Or more succinctly by Einstein, impudently quoted by Bergman et al.: “Common sense is the collection of prejudices acquired by age eighteen.”
8. There is also the matter of conflicts of interest. Dietrich et al. made no declaration of interests in their editorial, though later (CHE 18 Sept 2013) “he [Dietrich] acknowledged that he and many of his co-authors have extensive employment histories in industry, a status that could be seen by outsiders as affecting their credibility.” Declarations of interest are indeed about giving readers of a publication sufficient information to judge its credibility; since by his own admission the past and current affiliations of the authors “could” be seen as affecting its credibility, why did Dietrich et al. not state these interests in the editorial – especially since these are precisely the circumstances under which interests should be declared?