Persistent organic pollutants (POPs)
Biomonitoring of human milk for POPs
Since 1976 WHO through its GEMS/Food Programme has collected and evaluated information on levels of persistent organic pollutants in foods, including human milk. Over the period 1987-2003, it has coordinated three international studies of human milk to assess the levels and trends of polychlorinated dibenzodioxins, polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls. Analysis of human milk, maternal blood and adipose tissue are all relevant matrices for assessment of body burdens for persistent organic pollutants. However, human milk is recognized as the preferred matrix because has several important advantages. Biomonitoring of human milk data can provide information on the exposure of the mother as well as the infants. Furthermore, such information provide guidance on the need for measures to reduce levels of this substances in food, which is the main source of exposures for most people. More recently, it has been recognized that human milk is an ideal matrix to generally monitor levels of persistent organic pollutants in the environment.
In 2004, the Stockholm Convention on Persistent Organic Pollutants was ratified by governments to decrease environmental and human exposure to twelve priority substances in this class. The revised WHO guidelines for developing a national protocol describe the basic study design that can be used to monitor human exposure over time in order to, among other things, see if the Stockholm agreement is actually effective in reducing the release of these chemicals into the environment. These guidelines continue to support the monitoring of persistent organic contaminants for human health and food-chain contamination purposes. The protocol was designed based on the advice of experts in the field (see ad hoc WHO Human Milk Survey Advisory Group) and on extensive experience of certain countries in undertaking similar surveys using human samples, including human milk. In order to promote reliability and comparability, participating countries are encouraged to adhere as closely to this protocol as possible. Ethical issues, including informed consent of donors and confidentiality, are major considerations in this protocol. Given that breastfeeding reduces child mortality and has health benefits that extend into adulthood, every effort has been made to protect, promote and support breastfeeding in the context of these studies.