Ammonia build-up in animal boxes and its effect on rat tracheal epithelium

Some common laboratory species are now considered unsuitable for the study of the toxicity of inhalants because of the natural incidence of abnormal respiratory histology. Levels of ammonia commonly encountered in animal boxes and cages have been shown to cause histopathological changes in the tracheal epithelium of rats, and it is suggested that 'abnormal respiratory histology' could be a reflection of the standard of husbandry employed before and during an experiment.