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Posted by on in Centers of Excellence

Posted on behalf of Angie Perez

As of August 15, 2017, 29 states and Washington, D.C. have passed laws that legalize medical marijuana, and recreational marijuana is legal in eight states and Washington, D.C. These policy changes present new challenges for state regulators with respect to potentially increased impaired driving associated with marijuana use. A major hurdle in enforcing driving impairment laws is the lack of a standardized, non-invasive test that can determine a driver’s level of intoxication and impairment. Several calls for research have been put forth by various states (e.g., California and Colorado), as well as federal agencies (including the National Institute on Drug Abuse and the National Highway Traffic Safety Administration) in order to assist in determining impairment levels from marijuana use. Two companies, Hound Labs and Cannabix Technologies, are racing to develop and market instruments for detecting THC in breath (breathalyzer). While both companies have demonstrated that their devices are capable of detecting THC in breath, many challenges still exist in terms of correlating the concentration measured in breath with a driver’s impairment level.

A recent article by Lovestead and Bruno (2017) presented a three-pronged research approach for developing the “best” breathalyzer. According to the authors, these three prongs include: 1) providing fundamental data and models for the developing a breathalyzer; 2) studying the material properties in order to identify the best materials to “catch” and “release” THC; and 3) researching the chemical signature of breath that corresponds with intoxication (Lovestead and Bruno 2017). The authors found that THC and CB vapor pressures were two orders of magnitude lower than n-eicosane, a similar molecular weight compound with low vapor pressure, indicating that using surrogate data in models would have led to erroneous results. Ultimately, this finding illustrates the importance of having accurate fundamental data for developing and validating models. In light of this paper’s findings, then, although marijuana breathalyzers are near completion, ultimately identifying and establishing an impairment level will still require much work.

Cardno ChemRisk is evaluating methods based on existing published studies to model and correlate marijuana biomarker concentrations in blood with known metrics for behavioral and physiomotor impairment. Such pharmacodynamics-pharmacokinetic modeling and a better understanding of thresholds for physiomotor impairment will provide state regulators and law enforcement the necessary tools for adequately establishing and enforcing threshold impairment laws. If you would like to learn more about either these research areas, or our expertise in drug and alcohol pharmacokinetics and forensic toxicology, please contact Dr. Angie Perez or Dr. Ernest Fung.

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Posted by on in Centers of Excellence

Posted on behalf of Josh Maskrey.

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Posted by on in Centers of Excellence

Cardno ChemRisk’s publication “A human health risk assessment of lead (Pb) ingestion among adult wine consumers” was recently named one of the top three highly accessed articles in the International Journal of Food Contamination.  Cardno ChemRisk scientists analyzed Pb concentration in wines and modeled adult blood lead levels from wine consumption under various exposure scenarios based on national dietary survey data. Overall, our findings suggest that Pb content in wine does not pose a health risk to adult wine consumers.  You can read our original blog about this paper here.

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Posted by on in Centers of Excellence
Posted on behalf of Angela Perez, Paul Scott and Andrew Monnot.

The per- and polyfluoroalkyl substances, or PFASare a family of perfluorinated and polyfluorinated chemicals that have been used extensively since the 1950s in commercial applications, including surfactants, lubricants, paper and textile coatings, polishes, food packaging, and fire-fighting foams. Some of these PFAS, including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), persist in humans and the environment, and have been detected worldwide in wildlife. 

Two senior toxicologists at Cardno ChemRisk, Drs. Angie Perez and Andy Monnot, presented research on key PFAS exposure and risk assessment issues at the 2017 International DIOXIN Symposia, held in Vancouver, Canada from August 21 -25th.  Dr. Perez presented a meta-analysis of crop uptake factors for PFAS. The objective of Dr. Perez’s research was to provide a state-of-the science review on PFAS uptake in plants intended for human and animal consumption, and to conduct a screening level human health risk assessment for consumption of PFAS based on the following: i) in which crops PFASs have been detected; ii) at what concentrations are PFASs detected; iii) which PFASs have been previously detected in crops; and iv) where in the plant PFASs tend to accumulate, if at all. Additionally, known sources of PFAS deposition in soil and anticipated source deposition trends, based on commercial use patterns, were described.


Dr. Monnot presented a poster entitled An Evaluation of Federal and State Perfluorooctanoic acid (PFOA) Drinking Water Standards in the US.  The purpose of this research was to compare the federal and state drinking water standards for PFOA in light of the recent US EPA lifetime drinking water Health Advisory for PFOA of 0.01 µg/L.  A total of 10 PFOA drinking water standards were identified, ranging from 0.014 to 1.6 µg/L.  Each state used a variety of different assumptions to derive its PFOA drinking water standards. We found that only rarely was there any attempt to evaluate background exposures to PFOA; instead, most states employed a single “default” relative source contribution (RSC) factor, which may over-estimate PFOA’s true background exposures.  

A third poster, authored by Paul K. Scott, a senior risk assessor and expert statistician at Cardno ChemRisk with over 26 years’ experience, was presented by Dr. Monnot and titled A Probabilistic Evaluation of the 2016 U.S. EPA Health Advisory for Perfluorooctanoic Acid. The purpose of this analysis was to determine if some of the factors used to derive the US EPA health advisory for PFOA resulted in an overestimation of exposure and subsequent risk.  Specifically, Scott et al. determined that the relative source contribution (RSC) factor used by the US EPA is not consistent with the information in the scientific literature on background exposures to PFOA from non-drinking water sources. In this study, alternate values for the health advisory were calculated based on more realistic assumptions for the relative source contribution (RSC).  Using alternate values for the drinking water ingestion rate and the RSC resulted in health advisories for lactating women that ranged from 0.2 to 0.76 µg/L, and for the general population that ranged from 0.3 to 1.1 µg/L.  These results suggest that the US EPA used overly conservative assumptions when deriving its health advisory.

Cardno ChemRisk scientists have conducted numerous exposure studies and human health risk assessments pertaining to PFAS. Examples of Cardno ChemRisk’s key PFAS projects include a retrospective exposure assessment for PFOA; a critical review of the findings of the C8 Health Project panel; preparation of supporting documents for Canadian Soil Quality Guidelines; preparation of estimated daily intakes of PFAS from outdoor and indoor air, dust, soil, food, drinking water, and consumer products; and a hazard evaluation and human health risk assessment for a farm after 20 years of land application of biosolids. Cardno ChemRisk scientists also regularly present on the topic of PFAS. Recently, Dr. Perez presented a webinar with Earl Hagström of Sedgwick Law in San Francisco titled Beyond PFOA and PFOS — the Next Wave of Perfluorochemicals-Related Liability”. 

If you would like to learn more about our PFAS capabilities, please contact Paul Scott at This e-mail address is being protected from spambots. You need JavaScript enabled to view it  or Angela Perez at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .  
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Posted by on in Centers of Excellence

Posted on behalf of Rachel Novick and Alison Bowman. 

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