On October 1, 2026, the Agency for Toxic Substances and Disease Registry (ATSDR) announced the availability of two new draft Toxicological Profiles (ToxProfiles) for cadmium (Cd) and hexachlorocyclopentadiene (HCCPD). 91 Fed. Reg. 62518. ToxProfiles reflect ATSDR’s evaluations of the available literature on priority hazardous substances to provide important toxicological information to the public and health professionals. ATSDR has a statutory requirement under the Superfund Amendments and Reauthorization Act (SARA) to prepare ToxProfiles for each substance included on the Substance Priority List (SPL). The current SPL identifies 275 hazardous substances that ATSDR has determined pose the most significant potential threat to human health. The SPL is not a list of the most toxic substances, but, rather, a prioritization of substances based on their frequency, toxicity, and potential for human exposure at National Priorities List sites.
Cd is listed as the number three priority substance on the ATSDR SPL. Cd is an elemental metal found in nature and compounds made from Cd are used in many products, most frequently in nickel-cadmium batteries. Other uses include as a colorant in plastics, ceramics, and glasses, the production of some plastics and metal mixtures, and semiconductor materials in solar panels. The draft Cd ToxProfile reflects data published subsequent to the 2012 Cd ToxProfile and applies particle deposition modeling in the lungs to better characterize inhalation hazard.
Available data indicate that the respiratory system and developing nervous system are the most sensitive targets following acute and intermediate exposure, and the renal system is the most sensitive target following chronic exposure to Cd via inhalation. The renal, skeletal, and developing nervous system are the most sensitive targets of Cd oral exposure. ATSDR proposes a provisional chronic inhalation minimal risk level (MRL) of 1 ×10-4 mg Cd/m3 (0.1 µg Cd/m3) based on proteinuria (protein in the urine) in humans, an acute oral MRL of 0.002 mg Cd/kg/day based on proteinuria in rats, and a chronic oral MRL of 3 ×10-4 mg Cd/kg/day based on proteinuria in humans.
HCCPD is listed as the number 233 (of 275) priority substance on the SPL. HCCPD does not occur naturally, but it is manufactured and used to produce certain flame-retardant chemicals, pharmaceuticals, unbreakable plastics, and dyes. HCCPD was previously used to make certain pesticides that are now banned in the United States and most other countries. The draft HCCPD ToxProfile reflects data published subsequent to the 1999 HCCPD ToxProfile.
Available data indicate that the hematological and respiratory systems are the most sensitive targets of HCCPD inhalation exposure, and the gastrointestinal tract, renal system, and body weight are the most sensitive targets of HCCPD oral exposure. ATSDR proposes a provisional intermediate inhalation MRL of 1 ×10-4 ppm (1 ×10-3 mg/m3) and chronic inhalation MRL of 6 ×10-5 ppm (7 × 10-4 mg/m3) based on nasal discharge and inflammation in rats and mice, respectively, and an intermediate oral MRL of 0.06 mg/kg/day based on epithelial hyperplasia and localized inflammation in the forestomach in rats.
ATSDR ToxProfiles are relied upon routinely by governmental risk assessors across the globe as authoritative compilations of toxicological evidence. MRLs are not enforceable regulatory thresholds, but they are intended to serve as health-based reference values to inform risk assessments conducted by regulatory authorities. It is critical for product stewards to review the technical findings within ATSDR ToxProfiles and consider implications for their supply chain, product lifecycle management, and for worker, consumer, and public health.
Comments are due to the docket on December 30, 2026, at 11:59 p.m. (EST).
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