Assessment of Selected Persistent Organic Pollutants in Human Milk From Nairobi, Nandi, and Nyeri Counties, Kenya

Abstract

Persistent organic pollutants (POPs) are a group of chemicals that persist for long periods in environment without being degraded by natural means. They also have the tendency to build up in fat-containing foods as well as in human bodies; therefore, traces can be exposed in human milk (HM). POPs consist of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), among other halogenated organic compounds. Even though the bulk of POPs were prohibited or limited in Kenya in 1986, 1989, 2004, 2009, and 2011, reports continue to show their residues in the environment and human tissues. The aim of this study was to determine the levels of selected OCPs and PCBs in human milk (HM) samples, assess the health risks to exposed breastfed infants, and evaluation the possible sources of POPs in Nairobi, Nandi, and Nyeri Counties. HM samples were obtained from volunteer primiparas mothers in 11 maternal and child health clinics (MCHC) across Nairobi (3), Nandi (6), and Nyeri (2) Counties, Kenya. Study participants met selection criteria that included pre-sampling five years of continuous residency in the study location, be aged between 16 and 30 years old, be of apparent good health, be first-time mothers (primiparous), be a two- to eight-week lactation period, and be exclusively breastfeeding a single infant of apparent good health. A structured questionnaire was administered to each of the selected 116 mothers who subsequently offered HM samples. A replica of five grams of each of the individual HM samples was pulverized to a free-flowing powder with 25 grams of anhydrous sodium sulphate followed by Soxhlet extraction. The lipid content of each HM sample was determined gravimetrically using an aliquot of Soxhlet extract equivalent to 20%, while the 80% portion was cleaned up using aluminum oxide chromatography for GCMS/MS analysis. All HM (100%) samples from Nairobi and Nyeri counties, and 96.7% from Nandi County had quantifiable level(s) of one or more of; cis-chlordane, trans-chlordane, cis-nonachlor, trans-nonachlor, p,p’-DDD, p,p’-DDE, o,p’-DDT, p,p’-DDT, endosulfan ether, α-endosulfan, β-endosulfan, endosulfan sulphate, α-HCH, β-HCH, γ-HCH, δ-HCH, HCB, PCB#28, PCB#52, PCB#101, PCB#138, PCB#153 and PCB#180 compounds. The least occurring compound quantified in 1.69% of HM samples was endosulfan ether, whereas the most occurring compound quantified in 72.88% of HM samples was p,p’-DDT. The mean occurrence levels of the compounds ranged from 0.152±0.044 ng/g lw for trans-chlordane to 5.426±12.237 ng/g lw for p,p’-DDE. Aldrin, oxy-chlordane, o,p’-DDD, o,p’-DDE, dieldrin, endrin, endrin aldehyde, endrin ketone, heptachlor, cis(endo)-heptachlor epoxide, trans(exo)-heptachlor epoxide, mirex, pentachlorobenzene, and methoxychlor were below detection levels. The ratio of p,p’-DDE and p,p’-DDT (p,p’-DDE/p,p’-DDT) was 7.82, indicating a possible past exposure to the DDT group of compounds. DDTs and iPCBs were the major contaminants quantified in 86.44% and 55.08% of HM samples, respectively...