California DTSC Issues New Health Risk Assessment Guidance Regarding Arsenic Bioavailability Adjustment  (September 2016) 

The California Department of Toxic Substances Control (DTSC) recently released (August 22) guidance for taking into account the ingestion bioavailability of arsenic in human health risk assessments at contaminated sites. A chemical that is highly bioavailable via the ingestion route of exposure is well-absorbed into the body. Chemicals with low bioavailability are poorly absorbed. Previously, DTSC had normally required the assumption of 100% (maximum) bioavailability for arsenic in site health risk assessments. This assumption may result in an overestimate of arsenic health risks at sites where the geochemical form of arsenic on the site actually has a lower bioavailability. For example, arsenic at mine sites in particular often has a bioavailability significantly less than 100%. The guidance specifies an in vitro bioavailability test method, called the California Arsenic Bioaccessibility or CAB method. The CAB method can be applied to site soil samples and the results converted to the corresponding in vivo bioavailability using a linear regression developed by DTSC and its research partners. The resulting in vivo bioavailability value can then be used to adjust the arsenic health risk calculations for the site. DTSC notes that this bioavailability adjustment is most likely to make a significant difference in the risk estimates at sites where arsenic concentrations are less than 500 mg/kg.  Also note that high levels of arsenic at a site that are due to historical pesticide application, rather than mining activities, are less likely to benefit from this adjustment. A copy of the guidance is available at this link:

Risk Assessment News and Tips

 Advanced Assessment of Chemical Risks to Health and the Environment

Damian Applied Toxicology, LLC


Please see our News page for additional risk assessment developments and tips.

(530) 220-0454


  • Hazardous waste site human health and ecological risk


  • Veteran's disability claims due to chemical exposure (e.g. Camp Lejeune)

  • Vapor intrusion and indoor air health risk assessments

  • Medical toxicology case review

  • Expert witness and litigation support

  • Computational and predictive toxicology for novel chemicals and drugs using QSAR and read-across methods

  • California Proposition 65 compliance evaluations for

           consumer products

  • Food, cosmetic, and nutritional supplement safety
    including Generally Recognized as Safe (GRAS) expert panel participation 

  • Adverse effects of chemicals, drugs and dietary supplements

  • Drug-induced liver toxicity cases

  • Drug impurity risk assessment

FDA Issues Frequently Asked Questions Guidance Document for GRAS Food Additives/Ingredients

“Soluble nickel compounds” have been listed by the California Office of Health and Environmental Assessment (OEHHA) as a reproductive toxicant under California’s Proposition 65 (Prop 65) effective October 26, 2018. Soluble nickel compounds are those that are more soluble in water and include, for example, nickel chloride, nickel sulfate, nickel acetate, and nickel nitrate. On May 2, 2019, OEHHA issued a definition of soluble nickel compounds as those with a solubility in water greater than 0.1 moles per liter at 20°C. Soluble nickel compounds were listed on the basis of causing male reproductive toxicity and developmental toxicity. When a chemical is listed under Prop 65 as a reproductive toxicant compliance with Prop 65 can be evaluated based on comparison of daily consumer exposure to the Maximum Allowable Dose Level (MADL). If daily exposure for the typical user of the consumer product in question is below the MADL the product is in compliance with Prop 65. However, at the time of writing (Jan. 5, 2019) OEHHA has not yet developed an MADL for soluble nickel compounds. This may be developed in the future.

GRAS (Generally Recognized as Safe) refers to current food additives/ingredients and proposed food additives/ingredients that may be considered to be safe when added to foods, dietary supplements, or medical foods at specified levels for specified uses. A food additive/ingredient that has been determined to be GRAS need not go through the much more extensive FDA regulatory review process required for other food additives/ingredients. Food additives/ingredients may be determined to be GRAS if an expert panel, after reviewing relevant toxicity, usage and manufacturing information, determines the additive is safe per the proposed uses. FDA has published a Frequently Asked Questions guidance document that will be helpful to dietary supplement and other food additive companies that use the GRAS process. Dr. Damian has participated in numerous GRAS panels and is available to assist you with your GRAS review process. The guidance document may be found here:

California Proposition 65 Update - Soluble Nickel Compounds Listed

USEPA Issues Update of Regional Screening Levels 

USEPA issued the latest update of its Regional Screening Levels (RSLs) in June. The RSLs provide safe levels of exposure for hundreds of different chemicals in soil, air and water. The USEPA RSLs are the most widely used and cited health-risk based screening levels for chemicals in soil in the United States. They are also an important source of risk-based benchmarks for current or potential drinking water sources for which no drinking water standard (Maximum Contaminant Level or MCL) exists. To a lesser extent they are also sometimes used as a source of health-risk based chemical limits in ambient (outdoor) air and indoor air. It is important to always use the latest version of the RSLs when using the RSLs to perform a screening evaluation of health risks at contaminated sites. The update may be found here:

California Judge Strikes Down Hexavalent Chrome Drinking Water Standard

On May 31, 2017 a California judge struck down California's drinking water standard for hexavalent (hex) chromium. The California standard was the first drinking water standard for hex chrome in the United States. The 10 ppb standard (10 µg/liter) was first established in 2014 and took into account new toxicity tests which demonstrated that hex chrome was carcinogenic via the ingestion route of exposure in laboratory animals. The standard was invalidated because it did not take into account the economic feasibility of complying with the standard. Note that federal drinking water standards (Maximum Contaminant Levels or MCLs) are required to take into account economic and technological feasibility as part of the national drinking water standard setting process. This is also required under California state law. The judge ordered the development of a new standard, a process which typically takes 18 to 24 months. The state does not intend to appeal the ruling. In the meantime, the current standard for hex chrome will not be enforced. However, the drinking water standard for total chromium of 50 ppb (which includes both trivalent and hexavalent chromium) will remain in force and is unaffected by this ruling. 

Glyphosate Listed Under California Proposition 65

Effective July 7, 2017, glyphosate, the active ingredient in Roundup, and one of the most widely used herbicides in the world, was listed under California's Proposition 65 (Prop 65). It was listed as a carcinogen. A No Significant Risk Level (NSRL) of 1100 µg/day has also been proposed. An NSRL is the lifetime average daily chemical exposure level (intake) below which no Prop 65 warning is required for a particular consumer product or other chemical exposure situation. Further information may be found here:

California DTSC Finalizes Risk Assessment Guidance Note for Dioxin in Soils 

The CA Department of Toxic Substances Control (DTSC) has finalized a risk assessment guidance note (HERO Note Number 2) regarding soil remediation goals for dioxins. The guidance establishes remedial goals for dioxins in soil of 50 ppt (parts per trillion) for residential land use, 220-700 ppt for commercial/industrial use, and <40 ppt for agricultural use. The goals are expressed in units of Toxic Equivalents (TEQs). Units of TEQ are used to express the numerous dioxin-like compounds relative to the most toxic compound in this class (2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD). The note may be downloaded at the following link:

Welcome to our website! Damian Applied Toxicology, LLC (DAT) is a scientific consulting firm specializing in the advanced assessment of health and ecological risks related to chemical exposures occurring in the environment (e.g. Brownfield, mining, and hazardous waste sites), food, consumer products (e.g. dietary supplements, drugs, cosmetics, pesticides), and the workplace (e.g. workers' compensation cases). DAT also provides medical toxicology independent review services in cases involving drug use or chemical exposure.  

DAT uses state-of-the-science methods to independently and quantitatively evaluate potential health risks posed by chemicals to humans, wildlife and domestic animals. Typical clients of DAT include attorneys, mining firms, real estate developers, consumer product manufacturers, insurance companies, and environmental consulting firms seeking specialized expertise in the area of health or ecological risk assessment. These risk assessments can then be used by business decision-makers and regulatory agencies to determine appropriate mitigative measures if necessary to ensure adequate protection of public health and the environment. 

Paul Damian PhD, MPH, DABT, ERT is the Founder and Principal of DAT. He is a Board Certified Toxicologist (Diplomate of the American Board of Toxicology [DABT]) and European Registered Toxicologist (ERT - Royal Society of Biology, United Kingdom). Dr. Damian has 35 years of experience evaluating chemical risks to humans and the environment in a wide variety of chemical exposure circumstances and in numerous states across the country.

The main general service areas provided by DAT are shown below. Additional details are provided on our Services page.