Diphenylamine.

For its hazard assessment the committee took a 12-week study with oral administration of diphenylamine to mice as a starting pont. The critical effect is the formation of Heinz bodies (precipitated haemoglobin) in erythrocytes. From this study a no-observed-adverse-effect-level (NOAEL) of 1 mg/kg body weight per day is derived. To take account of differences between mice and humans a factor of 10 is introduced. For a man weighing 70 kg exposure to an oral dose of 0.1 mg/kg results in a daily intake of 7 mg. If it is assumed that retention after both oral and inhalatory exposure is 100%, exposure to a diphenylamine concentration in air of 0.7 mg/m3 results in a similar intake assuming that 10 m3 is inhaled during a 8 hour working day. The committee therefore recommends a health based exposure limit of 0.7 mg/m3 as an 8 hour time weighted average. It notes that at such a concentration the diphenylamine is present in in air in particulate form.