N-nitrosamines in laboratory animal feed and bedding

Area of Science:

• Analytical Chemistry
• Toxicology
• Laboratory Animal Science

Background:

• Volatile nitrosamines are a class of chemical compounds with known carcinogenic potential.
• Ensuring the safety of laboratory animal diets and bedding is crucial for the integrity of research findings.
• Previous studies have identified nitrosamines in some animal feed, but comprehensive analysis across different feed types and bedding is needed.

Purpose of the Study:

• To quantify volatile nitrosamine concentrations in commonly used laboratory animal feeds and bedding.
• To identify specific nitrosamine compounds present in these materials.
• To report previously unreported nitrosamines in laboratory animal feed.

Main Methods:

• Gas chromatography coupled with a thermal energy analyzer was employed for sensitive detection and quantification.
• Samples of various laboratory animal feeds (meal and pellet forms) and bedding materials were analyzed.
• Standard analytical procedures were used to identify and measure nitrosamine levels.

Main Results:

• N-nitrosodimethylamine was ubiquitously detected in NIH-07 and closed formula feeds, with varying concentrations in meal and pellet forms.
• Low levels of nitrosamines were found in hardwood chip and corncob bedding.
• N-nitrosodipropylamine, N-nitrosoethylmethylamine, and N-nitrosopyrrolidine were less frequently detected; the latter was absent in closed formula diets.
• N-nitrosodipropylamine, N-nitrosoethylmethylamine, and N-nitrosomorpholine were detected in a mineral mix sample, with the first two being novel findings in animal feeds.

Conclusions:

• Laboratory animal feeds and bedding can be sources of volatile nitrosamine contamination.
• The presence of these compounds, especially newly identified ones, necessitates careful consideration in animal research.
• Further investigation into the sources and implications of nitrosamine contamination in animal research supplies is warranted.