Environmental Assessments for Veterinary Drugs
Waterborne recently joined a leading global animal health company to assist the preparation of an Environmental Assessment (EA) to support the registration of a veterinary medicine for beef cattle. For new veterinary drugs to be approved for use, the FDA Center for Veterinary Medicine (CVM) conducts an EA to evaluate any potential ecological risks. This is a scientifically defensible characterization of risk based on the drug’s environmental exposure and toxicological effects. Like many other regulatory risk assessment paradigms, CVM’s framework is tiered allowing for realism and refinements to be brought in as needed at subsequent steps.
One of the projects key challenges was that a well-developed higher tier exposure assessment model for veterinary medicines did not exist. Waterborne was able to leverage their expertise in pesticide risk assessments to conceptualize and implement a novel methodology that was accepted by CVM and ultimately resulted in the approval of the registrant’s veterinary drug for use. Waterborne’s most significant contributions to the EA was the identification of the appropriate watershed-scale model to use in the assessment and the development of representative US beef cattle exposure scenarios by borrowing from the Tier 2 aquatic exposure characterization tools used in the EPA pesticide registration risk assessment process. The exposure modeling addressed three potential routes of overland transport to surface water from manure containing the drug (with related enhancements to the PRZM model); pasture cattle, feedlot cattle, and manured cropland in five representative beef cattle regions in the US. Specific modifications to winPRZM included two feedlot options: 1) constant soil concentration in the feedlot or 2) build-up of veterinary medications via daily applications which can be removed by specifying dates and amounts for scraping the feedlot. For pasture, the input file was modified to incorporate beginning and end dates for grazing (uses specified) which indicate daily applications.
By looking across commodity groups, the science used by regulators and registrants to assess the environmental safety of a veterinary drug was advanced. Other burgeoning industries grappling with solutions to higher-tier risk characterization may find plausible solutions in the mature pesticide market.