Comparing Water, Bovine Milk, and Indoor Residual Spraying as Possible Sources of DDTand Pyrethroid Residues in Breast Milk

The presence of pollutants in human breast milk is of major concern, especially in malaria control areas where 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) is currently used as indoor residual spray (IRS). The levels of DDT and pyrethroids (PYR) were determined in breast milk, bovine milk, and drinking water from northern KwaZulu-Natal, South Africa. Both reference and exposed mothers used the same market food, but the DDT levels in the exposed mothers (mean sigma DDT 10 g/g milk fat [mf]) were much higher than for the reference mothers (mean sigma DDT 1.3 g/g milk fat). This difference in residue levels indicates uptake from IRS-applied DDT, most likely via air and skin contact, and excludes food as the main source of pollutants. DDT levels in bovine milk (mean sigma DDT 0.15 g/g mf) from the exposed area were less than levels in breast milk from the reference area, and lower than the 20 g/L maximum residue limit (MRL) set by the Food and Agriculture Organization (FAO). Mean sigma DDT in water was 0.0065 g/L, much lower then the WHO limit of the sum of all metabolites in drinking water of 1 g/L, and therefore highly unlikely to have contributed to any extent toward levels in breast milk. Permethrin in breast milk (mean 1.1-1.6 g/g milk fat) was probably derived from home garden and indoor use, while the other PYR (cypermethrin and cyfluthrin) at lower concentrations were probably derived from food and agricultural exposure. It is postulated that a better understanding of the indoor dynamics of DDT and other insecticides, through a concept of Total Homestead Environment Approach (THEA), is crucial for investigating options of reducing human exposure and uptake under malaria control conditions.