Fred Ayodi Lisouza
Fred Ayodi Lisouza
School of Physical and Biological Sciences
RESEARCH TOPIC:
MONITORING AND CANCER RISK ASSESSMENT OF SELECTED
PERSISTENT ORGANIC POLLUTANTS IN NAIROBI CITY, KENYA
ABSTRACT:
In Kenya, cancer is the third cause of death, after infectious and cardiovascular diseases.
However, the causes of these high cancer burdens are not fully documented. Analysis of human milk
from Nairobi City revealed possible human exposure to bioavailable persistent organic pollutants
(POPs), which are known carcinogens. However, the levels, distribution, spatial variations and
sources of these bioavailable POPs in the city are not known. The Stockholm Convention on POPs
banned the use of eight organochlorine pesticides (OCPs), while USEPA monitors 16 priority
polycyclic aromatic hydrocarbons (PAHs) in the environment, due to their carcinogenic risks.
However, the cancer risks posed by environmental OCPs and PAHs to the residents of Nairobi City
have never been assessed. Use of passive sampling and active sampling in monitoring of
environmental OCPs and PAHs was evaluated. Levels of bioavailable OCPs and PAHs were monitored
in air and selected surface waters in Dandora, Kibera, City Square, Industrial Area and Ngong Forest
using semipermeable membrane devices (SPMDs) in a split-plot design replicated three times.
SPMDs were exposed for 28 days, extracted by dialysis and analytes fractionated by solid phase
extraction. The OCPs were analysed by GC-ECD while PAHs were analysed by GC-FID, and confirmed
by GC/MS. Analysis of variance was done, and the data used to determine the distribution, spatial
variation, sources, and cancer risks posed in Nairobi City. Active sampling gave lower (p≤0.05)
pollutants’ levels than passive sampling; indicating possible underestimation of their actual
environmental levels in previous studies. Adoption of passive sampling in monitoring of
environmental PAHs and OCPs is therefore recommended. Levels of gas-phase OCPs were