Rachel Shaffer is a research assistant.
Our mothers are no doubt on our minds right now, after Mother’s Day weekend. And I am no exception, especially since, as I blogged about last year, this month is the anniversary of my own mother’s breast cancer diagnosis.
This year though, in addition to celebrating my mother’s recovery, I can find hope in a new report from researchers at the Silent Spring Institute that provides guidance to improve our ability to screen for and study potential breast carcinogens — thereby enhancing efforts to prevent this widespread disease. Good news, certainly… and a timely gift for all of the women in our lives.
This new report describes biomonitoring methods for 102 breast carcinogens with high exposure potential and identifies existing cohort studies into which these methods could be integrated immediately. These chemicals are among the 216 previously identified by the authors as chemicals linked to mammary gland tumors in rodents. By testing for exposure markers of these priority breast carcinogens in the population, researchers should be able to better identify and study high-risk groups, and regulators will be better able both to limit dangerous exposures and to demonstrate the public health benefits of these exposure reductions.
The full report is available online, but I want to highlight a few key themes that are particularly relevant to current scientific and political debates.
The value of predictive toxicology, and the need to act
The chemicals of concern in this publication were flagged based on existing animal toxicological evidence. However, in the ongoing efforts to assess the health effects of common chemicals, toxicology and epidemiology may – at times – seem to be discordant. One stream of evidence may be strong, while the other is inconclusive (or yet unexplored). In such cases, it can be challenging for scientists and regulators to come to a decision about hazard and risk.
However, as EDF has warned previously, decisions delayed result in real-world public health consequences. As noted in this new publication, about one-third of all known carcinogens were demonstrated to be carcinogenic in animals before such evidence was available from human epidemiological studies. While there may be very important differences in potency or target site between animals and humans, it is critical to act appropriately to protect public health when sufficient animal toxicological evidence exists. [Note: There may also be a need to act when epidemiological evidence is strong but toxicological evidence is still inconclusive.] Researchers from the International Agency for Research on Cancer (IARC) similarly concluded that “every Group 1 [IARC’s highest classification level, “carcinogenic to humans”] agent can be considered to represent cancers that might have been prevented had scientists been able to predict hazard earlier or had public health authorities been willing to act more quickly when scientific information became available.”
Endocrine-disrupting chemicals (EDCs) as potential breast carcinogens, and the need for better testing
Research on breast carcinogens has traditionally been conducted using standard rodent cancer bioassays. However, emerging research suggests that some chemicals may increase the risk of breast cancer through their endocrine-disrupting properties, which traditional cancer bioassays may not capture. Hence, we need new testing methods – animal, in vitro, and in silico - that can adequately assess these endocrine-disrupting effects, so that chemicals on the market can be appropriately screened.
Ubiquity of breast carcinogens, and the need for chemical policy reform
In this publication, researchers identified 102 chemicals as priority breast carcinogens due to high exposure potential in the population. Most of these chemicals can be grouped into 17 categories, and a table following the report provides detailed information on the chemicals, their exposure sources, and relevant biomarkers. Several examples of such chemicals and their main uses or exposure sources are below:
1,3-butadiene: gasoline, vehicle exhaust, tobacco smoke, heating of cooking oils
Aromatic amines: spray-insulation, polyurethane foam, sealants and coatings, hair and textile dyes, paints, printing inks
Benzene: gasoline, vehicle exhaust, tobacco smoke, solvents
Endocrine disruptors: consumer and commercial products with hormonal activity
Flame retardants and breakdown products: flame-retardant plastics and foams
Perfluorinated compounds: grease/water/stain-resistant coatings, contaminated water
Styrene: building materials, polystyrene food packaging, indoor air, cigarette smoke
Glancing over this list, we are again reminded of the pervasiveness of dangerous chemicals in our environment. These toxic chemicals are all around us – we encounter them in common products and everyday situations. Many of these toxic chemicals are in us – they have been detected by national surveillance and biomonitoring programs. And finally, many of these toxic chemicals are made or imported in large quantities – a recent EDF report, Toxics Across America, identifies the numerous sites of manufacture or import of very-high-production-volume toxic chemicals in this country. (With this map tool, you can search for chemicals that were highlighted in the Silent Spring report using the CAS numbers provided in the associated supplementary materials; you may be shocked at what you find).
The ubiquity of these toxic chemicals emphasizes the need for chemical policy reform. Since last Mother’s Day, we’ve seen important movement in the Senate, and more recently in the House, towards reforming the Toxic Substances Control Act (TSCA). While major improvements are still needed in these bills before adoption, we cannot forfeit this opportunity to create a more effective and efficient system that will better protect all of us, including the women in our lives, from potentially harmful chemical exposures.
On the road to better science, better policy, and better health
Together, the roadmap for improving scientific biomonitoring described in the new Silent Spring report, coupled with better testing approaches to identify dangerous chemicals and stronger federal regulatory policies, should help to open a much-needed path to better health.
And that would be a Mother’s Day gift that keeps on giving, year after year.