RESUMEN
Monitoring of human milk samples for the presence of chemical contaminants has been carried out in Canada for several decades. In 1986-87 over 400 donations of human milk were collected nationwide and 100 of these, selected by province according to population, were analysed for the PCDDs/PCDFs. The results show the presence of about eleven different analytes all with 2,3,7,8-substitution with the PCDDs at higher and more variable concentrations than the PCDFs. On a 2,3,7,8-TCDD toxic equivalents (TEQ) basis, the mean value for the country is about 15 ng per kg milk fat. This TEQ value is similar to that from many other industrialized nations and about 50% lower than certain European states. Little or no variation was apparent in the milk content among the various Canadian provinces probably reflecting the uniformity of the general food supply across the country. Limited data over a period of five years suggest the average level of these compounds in human milk may be decreasing.