Organochlorine pesticide residues in human milk of a Hmong hill tribe living in Northern Thailand.

In December 1998 whole breast milk samples from 25 Hmong mothers living in the village of Mae Sa Mai, 40 km north of Chiang Mai City, Northern Thailand, were collected and analysed for DDT, heptachlor, HCB and HCH residues (fat normalized data). Short questionnaires and anthropometric measurements were used to obtain information on personal characteristics, lifestyle, contact with pesticides, dietary habits and former residences. DDT was detected in all samples with a median and maximum level of 209 and 2012 ng of total DDT isomers per millilitre of milk, respectively. The median and highest percentages of p,p'-DDT were 23.2 and 44.7%. In 15 samples heptachlor was detected in the metabolized form of heptachlor-epoxide with a median value of 4.4 ng/ml. The estimated daily intakes of DDT, heptachlor and heptachlor-epoxide by the infants exceeded up to 20 times the acceptable daily intakes as recommended by the FAO and WHO. In nine samples HCB was detected with a median value of 5.4 ng/ml from which seven of the nine also had the highest values of DDT residues. The gamma-isomer of HCH was only found in one sample with 3.6 ng/ml. The mean sum-DDT residues with 14.96 mg/kg milk fat, as well as the estimated daily intakes by the infants are one of the highest reported in the 1990s. The fact that the mother breast-feeds her first child and that she originally comes from a region where DDT is still in use as a vector control agent, as well as the former use of organochlorine pesticides (OCPs) in agriculture, seem to be the main factors for high DDT and other OCP residues in the mothers' milk.