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Melanie Nembhard

Melanie Nembhard

Ms. Melanie Nembhard is an Associate Health Scientist with Cardno ChemRisk in the San Francisco, CA office. She earned her MSPH in Occupational and Environmental Hygiene from the Johns Hopkins Bloomberg School of Public Health. She also holds two certificates from Johns Hopkins, the Risk Sciences and Public Policy Certificate and the Population and Health Certificate. Ms. Nembhard’s principal areas of training and expertise include industrial hygiene and risk assessment. Since joining Cardno ChemRisk, she has provided litigation support for cases related to asbestos, benzene, butadiene, diacetyl, worker safety, welding, sunscreen, dermal exposures to various chemicals, and inhalation irritants. Additionally, she has participated in baseline exposure assessments at multiple oil refineries regarding occupational and environmental exposures to various chemical and physical agents, including particulates, volatile organic compounds, and noise.

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 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
We are pleased to share with you an article our colleagues recently published in Inhalation Toxicology, titled “Cosmetic talc as a risk factor for pleural mesothelioma: a weight of evidence evaluation of the epidemiology.

In this paper, the authors pooled all of the mesothelioma studies of cosmetic talc miners and determined that, if in fact mesothelioma incidence had been significantly increased in these cohorts, it would have been detected using standard statistical techniques.  No increase at all was observed, and in fact there wasn’t a single reported case of mesothelioma in any cohort. 

The impetus for this study was a statement by EPA (in the early 1990’s) that the existing data were not sufficiently powerful to assess whether the miners were at risk.  Our analysis, which relies primarily on findings published since that time shows that there is now sufficient power to make such a determination.  As described in the paper, our findings are consistent with the fact that no pleural mesotheliomas have been observed in patients treated with very high doses of cosmetic talc placed directly in the pleura (“pluerodesis”).

Because miners were exposed to cosmetic talc at levels much higher than those associated with the use of cosmetic talc products, we conclude this is evidence that product use is highly unlikely to be a risk factor for mesothelioma.

If you have any questions or would like further information, please contact Dr. Stacey Benson.
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Posted by on in Centers of Excellence

June 3rd and 4th, three employees of Cardno ChemRisk participated in the Avon walk to end breast cancer.  The Avon walk to end breast cancer occurs in seven US cities every year and asks each participant to raise at least $1800 and to walk 39.3 miles over the course of two days.  It started in 2003 and to date has raised over $600 million.  This is Laura Beth’s second year walking in memory of her Grandma Schwab, who lost her battle to breast cancer 20 years ago, and in honor of her sister-in-law, Hannah, who was diagnosed two years ago (and who is doing great!).   This year #TeamHanna (Laura Beth Miller, Laurie Armijo and Stacey Benson) raised over $11,000 and completed all miles of the walk in Chicago.  The Chicago event collectively raised over $3.1 million.  The money raised for this event will be used to “accelerate breast cancer research; improve access to screening, diagnosis and treatment; and educate people about breast cancer”.  

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Posted by on in Centers of Excellence
Posted on behalf of the author Paul Scott

Environmental Protection Agency (EPA) Administrator Scott Pruitt on May 10, 2017 issued a memorandum revising the existing delegations of authority related to the approval of proposed remedies at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), or “Superfund” sites. In the memorandum, EPA Administrator Pruitt reserved his authority to make the remedy selection at CERCLA cleanup sites whose Record of Decision (ROD) had a proposed cleanup cost exceeding $50 million.   In the past, remedy selection decisions at these sites were performed by the Assistant Administrator for the Office of Land and Emergency Management and the Regional Administrators.  The stated purpose of Administrator Pruitt's delegation of this authority to his office for these sites was to improve the remedy selection process and to involve the Administrator and his office in the remedy selection process more directly.

This change in remedy selection authority will have a direct impact on contaminated sediment sites where the proposed remedy is often in the hundreds of millions of dollars let alone greater than 50 million dollars.  For most of the major contaminated sediment Superfund sites, the selected remedy will have to be approved by the Administrator instead of by a Regional Administrator or Assistant Administrator for the Office of Land and Emergency Management.  For perspective, the proposed costs for the remedies for the following sediment sites from their respective RODs:

  • Hudson River: $460 million 
  • Passaic River: $1.38 billion 
  • Fox River: $390 million
  • Lower Duwamish River: $342 million
  • Portland Harbor: $1.05 billion

The announcement and a link to the memo are located on the EPA website here.
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Cardno ChemRisk is a respected scientific consulting firm headquartered in San Francisco with locations and consultants across the U.S. While our website provides a formal look at our capabilities, the Cardno ChemRisk View provides an informal voice too. Various Cardno ChemRisk consultants will be sharing news and views about current trends, happenings and methodologies in the industry. We’ll also highlight activities of interest at Cardno ChemRisk, within confidentiality restrictions of course.

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