Evaluation of potential human health risk associated with consumption of edible products from livestock fed ration supplemented with Red Lake Diatomaceous Earth

ABSTRACT

Red Lake Diatomaceous Earth (DE) is a naturally occurring blend of diatomaceous earth and calcium bentonite that can be used as an anti-caking agent in animal feed and contains naturally occurring dioxins. A quantitative risk assessment was conducted to assess potential human health risk associated with consumption of edible tissues from livestock exposed to dioxins via feed containing Red Lake DE. Empirical data characterising the transfer of dioxins to eggs and other tissues in chickens demonstrate that resulting concentrations in eggs are lower than those found in the general food supply. These data also provided product-specific input for a risk assessment conducted both with default parameters and with media-specific input from the feed study. Results demonstrate that exposure to dioxins in edible tissue from livestock that consumed Red Lake DE in feed would not be associated with an increased risk to humans. Findings from this assessment highlight the utility and importance of accounting for bioavailability as part of health-based risk assessment and provide information critical to risk managers in determining the safe use of Red Lake DE as an anticaking agent in livestock and pet feed.

Graphical Abstract

KEYWORDS:

• Livestock
• feed
• dioxins
• TCDD
• PCBs
• chickens
• eggs
• risk assessment

Acknowledgments

The authors thank Steve Soderstrom, Gavin Boylin, Eva Borgman, Brian Cheng, Rich Duong, Kayla Erath, Katherine Gardner, Mieko Temple, and the staff of Cal Poly Poultry Unit for their assistance with the chicken feed study.

Disclosure statement

Dr. Wikoff has served as a testifying expert in a litigation case in Oregon for Absorbent Products Ltd., on this topic; her testimony covered only the risk assessment using OEHHA defaults (because the media-specific information from the chicken study had not yet been conducted at 710 the time). Dr. Wikoff, Mr. Brorby, and Ms. Franke were not involved in the design or conduct of the chicken feed study.

The researchers’ scientific conclusion and professional judgements were not subject to the funders’ control; the contents of this manuscript reflect solely the view of the authors.

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

ToxStrategies is a private consulting firm providing services on toxicology and risk assessment issues to private and public organizations. The firm’s efforts for conducting the research and drafting the manuscript were sponsored by Absorbent Products Ltd.; no ToxStrategies authors received personal fees. Dr. Bennett’s efforts in conducting the chicken feed study and associated costs were sponsored by Absorbent Products Ltd.