It is not pure and can contain several chemicals residues and few heavy metals. Still, our recommendation is to breastfeed as long as you can because the advantages are more than the disadvantages.
All the breast milks in this world contain residues of DDT or their metabolites, other pesticide residues and pollutant toxins such as dioxins. Polychlorinated biphenyls (PCBs), polychlorinated dibenzofuranes (PCDFs), polybrominated biphenyls (PBBs) and polybrominated diphenylethers (PBDEs) are also often present. These are accumulated in the fat of the human beings. The simple way to minimise this risk is to increase the weight of the mother so that more body fat is available for the same amount of chemical residues in her body, thus the fat of the breast milk also contains less pesticide residues. This should be carefully planned with the help of your doctor and dietician because factors such as pregnancy high blood pressure and diabetes must be considered very cautiously.

Diet is a main factor which influences breast milk levels of persistent organic pollutants which come from fish consumption or living near agricultural land where pesticides and other chemicals are indiscriminately used.