RESUMO
The degree of exposure by nursing mothers to individual polychronated biphenyl (PCB) congeners was studied and an estimate made of the daily intake by their infants. Epidemiological data from 100 nursing mothers were collected; 11 individual PCB congeners were determined in samples of the mothers' milk and the toxicity equivalent (TEQ) calculated. The mothers' data and the congener levels were statistically correlated. In over 80% of the samples, PCB congeners nos 180, 28, 138 and 170 were identified, and in over 70%, PCB congeners nos 188, 52, 187 and 153. PCB congeners nos 183, 101 and 118 were identified in percentages of between 39 and 15% of the samples. The highest levels detected were those in PCB no. 28 (1.626 ppb), and the lowest concentrations corresponded to PCB no. 183 (0.109 ppb). The toxicity equivalent (TEQ) was calculated from the toxic equivalent factor (TEF) of the congeners studied. There were no statistical differences between the geographical place of residence, age, occupation, and the congeners studied. There was a significant differentiation with respect to the birthplace, the location of industrial estates and the irrigation facilities in the area of residence, to smoking, the consumption of a varied diet, meat, fish or industrially processed foods, the physical constitution of the mothers, number of children and lactation periods, and PCB congener levels. The total PCB daily intake estimate was under the acceptable daily intake (ADI) limits of tolerance (WHO, 1988), and it was not possible to come to any conclusions for the estimated daily intake (EDI) of the 11 congeners studied since these have not yet been established. It was thus proposed to use the EDIs obtained in order to establish the ADIs of the individual PCB congeners.