Temporal Trends of Persistent Organic Pollutants across Africa after a Decade of MONET Passive Air Sampling

The Global Monitoring Plan of the
Stockholm Convention on Persistent
Organic Pollutants (POPs) was established to generate long-term data
necessary for evaluating the effectiveness of regulatory measures
at a global scale. After a decade of passive air monitoring (2008–2019),
MONET is the first network to produce sufficient data for the analysis
of long-term temporal trends of POPs in the African atmosphere. This
study reports concentrations of 20 POPs (aldrin, chlordane, chlordecone,
DDT, dieldrin, endrin, endosulfan, HBCDD, HCB, HCHs, heptachlor, hexabromobiphenyl,
mirex, PBDEs, PCBs, PCDDs, PCDFs, PeCB, PFOA, and PFOS) monitored
in 9 countries (Congo, Ghana, Ethiopia, Kenya, Mali, Mauritius, Morocco,
Nigeria, and Sudan). As of January 1, 2019, concentrations were in
the following ranges (pg/m3): 0.5–37.7 (∑6PCB), 0.006–0.724 (∑17PCDD/F), 0.05–5.5
(∑9PBDE), 0.6–11.3 (BDE 209), 0.1–1.8
(∑3HBCDD), 1.8–138 (∑6DDT),
0.1–24.3 (∑3endosulfan), 0.6–14.6
(∑4HCH), 9.1–26.4 (HCB), 13.8–18.2
(PeCB). Temporal trends indicate that concentrations of many POPs
(PCBs, DDT, HCHs, endosulfan) have declined significantly over the
past 10 years, though the rate was slow at some sites. Concentrations
of other POPs such as PCDD/Fs and PBDEs
have not changed significantly over the past decade and are in fact
increasing at some sites, attributed to the prevalence of open burning
of waste (particularly e-waste) across Africa. Modeled airflow back-trajectories
suggest that the elevated concentrations at some sites are primarily
due to sustained local emissions, while the low concentrations measured
at Mt. Kenya represent the continental background level and are primarily
influenced by long-range transport.