Cadmium in breakfast cereals, PFAS in drinking water, food additives in processed meats. Almost every month, new evidence of exposure to potentially carcinogenic substances emerges and ends up making headlines. But a question often remains in the background: who decides whether a substance is carcinogenic?
And above all, how is it possible that thousands of chemical compounds arrive on the market without their health effects having been thoroughly evaluated?
To ask the question is Valentin Thomassociologist and political scientist at the CNRS (French National Center for Scientific Research), who has been studying the mechanisms for assessing carcinogenic risks for over ten years. In an interview with Reporterrethe scholar denounces the flaws in a system that often allows the marketing of substances that are poorly or not tested at all.
According to an estimate by the French National Cancer Institute (Inca) and the IARC, just 4% of cancers diagnosed in France are attributable to industrial exposures, compared to 28% linked to smoking and alcohol.
But this data, warns Thomas, should be read with caution: to make the estimate, just around forty chemical substances were considered, a minimum number compared to the approximately 350 thousand present on the global market today. Rather than photographing the real weight of industrial pollution, that 4% highlights above all the scarcity of available information.
Substances on the market without extensive testing
In the European Union, assessment requirements depend on the quantities produced or imported. For many substances marketed in low or medium volumes, specific carcinogenicity tests are not required, while more in-depth studies become mandatory only beyond certain production thresholds.
As a result, numerous compounds may arrive on the market without their potential long-term effects having been truly clarified.
Further complicating the picture is the fact that many toxicological studies are carried out or financed by the manufacturing companies themselves. Often only the final results are published, without making data and methodologies accessible, making independent verification difficult.
The PFAS case and the limits of controls
PFAS represent perhaps the most emblematic example. Used for decades in many industrial sectors, today they contaminate water, soil, food and even human blood. For some of these compounds the toxicity is now established, while for thousands of others sufficient data is still lacking. Yet, they remained off the regulatory radar for years, in part because the rules did not mandate mandatory testing for entire categories of substances.
IARC can’t keep up
The IARC, the World Health Organization agency that classifies carcinogenic substances, represents a fundamental scientific reference point. But it must be said that, since 1971, it has evaluated less than 1,100 exposures, compared to over 350 thousand chemical substances in circulation.
Not only that: much of the agency’s work now consists of updating existing assessments. The result is that the ability to analyze new substances grows much more slowly than the speed at which they are brought to market. Furthermore, according to Thomas, some industries deliberately fuel scientific uncertainty by funding studies with conflicting results, making it more difficult to reach definitive conclusions and delaying any restrictions.
Even when a substance is classified as carcinogenic, the ban is not automatic. The case of glyphosate is emblematic: in 2015 the Iarc defined it as “probably carcinogenic“, but then gave rise to a plurality of opinions which practically often allowed political decision-makers to choose the interpretation most favorable to the continuation of the use of a substance. Thus, in 2023, the EU renewed the authorization of glyphosate for another ten years.
The researcher’s conclusion is as simple as it is disturbing: today we know the risks of PFAS, glyphosate or cadmium because someone has studied them. But for hundreds of thousands of other substances present in the environment and in the products we use every day, information is still insufficient. And the absence of evidence of danger does not at all equate to proof of their safety.
