Toxicology & Risk Sciences

Gradient evaluated potential health effects of polychlorinated biphenyl (PCB) in a metropolitan waterway.  We reviewed and analyzed the regulatory criteria, scientific literature, and historical state of knowledge regarding human and animal effects of PCBs.  We also calculated potential human PCB exposures and risks to people residing near, engaging in recreational activities near, and eating fish from the affected waterway.

For a critical infrastructure industry client involved in manufacturing construction products, energy equipment, and transportation products, Gradient evaluated occupational stewardship practices and provided guidance on best practices for worker protection in the context of the COVID-19 pandemic.  Gradient provided a summary of best practices for COVID protection for workers, with specific focus on respiratory protection and social-distancing protocols.

Gradient evaluated whether occupational exposure to toluene diisocyanate (TDI) via inhalation and dermal contact is a causal factor in acute myeloid leukemia (AML).  We critically reviewed epidemiology, experimental animal, and genotoxicity/mutagenicity studies of TDI in the context of AML.  We also evaluated the literature on latency periods following chemical-induced AML.

Gradient has provided toxicology and risk assessment support, including regulatory comments, for numerous clients related to PFAS substances.  We have evaluated potential exposures and health effects from PFAS in drinking water and consumer products, and the health protectiveness of state and federal drinking water values for various PFAS.  We have also derived health-protective PFAS reference doses and drinking water levels.

Gradient has provided toxicology and risk assessment support for numerous clients related to TSCA risk evaluation and risk management processes.  We have assessed a number of chemicals, including asbestos, carbon tetrachloride, tetrachloroethylene, trichloroethylene, and methylene chloride.  We have evaluated manufacturing processes and occupational exposure information.  We have also provided comments on the proposed toxicity criteria and existing chemical exposure limits (ECELs) for many of these chemicals, in addition to the systematic review process applied by US EPA for hazard evaluations.

Gradient provided regulatory comment on a proposed ambient water quality criterion (AWQC) for manganese.  Gradient critiqued the proposed AWQC using updated research from physiologically based pharmacokinetic models, derived an AWQC consistent with the current science, and performed a risk assessment to determine its adequacy to protect public health.  Gradient also provided comments in a public hearing.