They said the low dosages of radiation workers were exposed to also underlined the priority given to safety.

BBC: Dounreay nuclear site's safety 'improving'

Warren Zapol, of the Massachusetts General Hospital and a professor of anaesthesia at Harvard Medical School, along with his colleagues, monitored the vital signs of mice exposed to low-dosages (80 parts per million) of hydrogen sulphide for several hours.

ECONOMIST: Researchers find hydrogen sulphide can lower metabolism

Experts have blamed the rise on the incorrect use of poisons where dosages which are too low have been used.

BBC: Rats