EPA finds 1,2-dichloropropane, a known carcinogen, an unreasonable health risk

The U.S. Environmental Protection Agency published a draft risk evaluation on 4 September for 1,2-dichloropropane, an industrial solvent, and preliminarily determined that the chemical "does pose unreasonable risk to human health" under certain conditions of use [s1]. The public comment period runs until 3 November 2026 [s1].

That is a consequential finding in EPA's own regulatory language. Under the Toxic Substances Control Act, a risk evaluation asks a narrow question — whether a chemical presents an unreasonable risk of injury to health or the environment, judged without regard to cost — and a preliminary determination of unreasonable risk is the step that can eventually lead to restrictions on how a chemical is used [s1].

What the chemical is and where people meet it

1,2-Dichloropropane is not obscure. Its aggregate U.S. production volume is between 100 and 250 million pounds, and additional quantities may be imported [s1]. Industrial and commercial uses include processing as a reactant, laboratory chemical use, and cleaning and furnishing-care products [s1].

The exposures EPA is most concerned about are occupational. Workers and "occupational non-users" — people who work nearby but do not handle the chemical directly — may be exposed by inhalation, and workers may also be exposed through the skin during manufacturing, processing, use or disposal [s1]. In the draft, EPA assessed risks not only to workers but to consumers and to the general population, including "fenceline communities" living near facilities that release the chemical [s1]. It evaluated both cancer and non-cancer risks across acute, intermediate and chronic exposures [s1].

The evidence that this is a human carcinogen

The cancer half of that assessment does not rest on animal data alone. The International Agency for Research on Cancer classifies 1,2-dichloropropane as carcinogenic to humans — Group 1, its highest certainty category [s2]. That classification is unusual in its origin: it was driven by the identification of a cluster of biliary-tract cancers, specifically cholangiocarcinoma, among workers at a printing company, first reported by Kumagai and colleagues in 2013 [s2].

The circumstances of that cluster are worth stating plainly because they explain both the strength of the evidence and its limits. 1,2-Dichloropropane had come into common use as a cleaner in offset-printing processes in Japan, and the affected workers removed ink under conditions of high, sustained exposure [s2]. A real-world occupational cohort developing a rare cancer is the kind of "sufficient evidence in humans" that IARC treats as decisive — but it also describes an exposure setting far more intense than most consumer contact.

How to read a draft, and what comes next

Several cautions belong on this story. First, the determination is a draft. EPA is explicitly seeking comment and additional data, including monitoring data and information on protective equipment and engineering controls used across specific occupational scenarios [s1]. The agency also released a separate draft chemistry, fate, release and exposure assessment in July 2026 that feeds into this evaluation [s1]. The findings can change before they are finalised.

Second, "unreasonable risk" is a legal threshold, not a measure of everyday personal danger. It is driven, in EPA's phrasing, "primarily by certain conditions of use" [s1] — meaning the risk is concentrated in particular industrial and commercial settings rather than spread evenly across the population. The evaluation does not tell an individual reader what their own exposure is, and this article does not offer health advice.

What it does mark is a step in a slow regulatory pipeline. A finalised unreasonable-risk determination would obligate EPA to manage that risk, which is where any actual limits on manufacturing, use or disposal would be set. For now the substantive news is the direction of EPA's preliminary judgment on a high-volume chemical that an independent WHO body already regards as a proven human carcinogen — and the open comment window in which that judgment can be contested with data.

Sources

• [s1] U.S. Environmental Protection Agency, "1,2-Dichloropropane Draft Risk Evaluation Under the Toxic Substances Control Act (TSCA); Notice of Availability and Request for Comment," Federal Register, 4 September 2026.
• [s2] International Agency for Research on Cancer, IARC Monographs Volume 110, "1,2-Dichloropropane," 2017.