P-aminophenol excretion as an index of aniline exposure.

In view of the fact that aniline is absorbed not only by inhalation but also through the skin, the aerial contamination alone is not an exact indication of exposure. It is necessary to find a biological test which reveals exposure and is independent of the route of absorption. It is conceivable that the p-aminophenol excretion in the urine, which is a well-known symptom of aniline intoxication, can fulfil this requirement. However, it is doubtful whether the p-aminophenol reaction will allow the degree of exposure to be assessed. At the International Congress on Occupational Health held in Helsinki Dr Magos and the present author stated that methaemoglobin values above 0·5 g per cent indicate an increased, acute exposure. In experiments on the inhalation of aniline with ourselves as subjects, we found that p-aminophenol excretion is also a symptom of acute aniline exposure. With this information we carried out a study to relate the urine p-aminophenol values to methaemoglobinaemia in order to estimate the value of the p-aminophenol excretion as an index of the degree of aniline exposure. In the course of this study we determined the p-aminophenol in the urine, and the methaemoglobin in the blood, of persons working in aniline factories. The samples were taken at the end of the working shifts. Methaemoglobin was estimated in a Pulfrich photometer by the method of Magos and Szirtes-, p-aminophenol was determined by the Greenberg and Lestermethod as modified by 1. Batskor", It was found that, if the methaemoglobin values were less than 0·5 g per cent, the maximum p-aminophenol value was under 12 mgjl, of urine, the average being 2 '08-2·7. When the methaemoglobin values were between 0·5-2-0 g per cent, the p-aminophenol in the urine varied from 8,0-62,5 mg/l, with an average of39·44 ± 20·0mg/I. Above2·0gpercentmethaemoglobinaemia, the p-aminophenol values varied between 27 ·0-630,0 mg/L, with an average of 236·0 ± 210·0 mg/L Since the methaemoglobin values under 0·5 g per cent represent slight exposure, the corresponding figures ofp-aminophenol excretion, i.e., under 12·0 mg/l., also show slight exposure. The exposure is increased if the methaemoglobin values lie between 0-5-2·0 g per cent, and therefore the corresponding p-aminophenol values also represent an increased exposure, (The majority of the figures. falls between 19-59 mg/l.) In those cases in which the p-aminophenol values exceed 50-0 mg/l., the exposure is' certainly serious, since the methaemoglobinaemia is above the toxic limit, One must even reckon here with the possibility of poisoning, but it has to be