Air monitoring of brominated flame retardants in Gauteng Province, South Africa.
Katima, Zainab Jamidu
Katima, Zainab Jamidu
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Abstract
Brominated flame retardants (BFRs) are organobromine chemicals that have an inhibitory effect on combustion chemistry; they are added to consumer products to make them less flammable in order to minimise fire-related damage and deaths. The literature has shown that some BFRs possess similar properties to known persistent organic pollutants (POPs). Certain POPs are known to undergo long-range atmospheric transport, they bio-accumulate, and have the ability to cause potential adverse effects on living organisms. Consequently, the major congeners of polybrominated diphenyl ether (PDBE), namely commercial pentaBDE and octaBDE, were listed under the Stockholm Convention on persistent organic pollutants (POPs) in 2009. Recently, commercial decaBDE has also been added to the list of POPs due to concerns related to its possible degradation to lower brominated congeners that are more toxic and persistent in the environment. Despite the global restrictions on the manufacture of certain PBDEs, particularly in most developed countries, they are still being detected at elevated levels in different environmental matrices. With respect to the atmospheric burdens of most BFRs, particularly PBDEs, hexabromocyclododecane (HBCDDs), tetrabromobisphenol A (TBBPA) and alternative flame retardants (AFRs), there is still a paucity of information in the entire Southern Hemisphere. This presents a challenge in terms of gaining a regional perspective of these pollutants in the atmosphere.
Previous studies in South Africa have reported the occurrence of PBDEs, HBCDDs and AFRs in different environmental matrices. These reports demonstrate the presence of BFRs in the South African environment. However, to date there are no published studies in Africa, including South Africa, on the levels and sources of atmospheric BFRs in the urban and industrial areas as well as landfill sites. Hence, the major objective of this study was to measure the atmospheric concentrations of PBDEs, HBCDDs and selected AFRs in Gauteng Province, South Africa, using passive air samplers. Polyurethane foam passive samplers were deployed between May 2016 and May 2017 to evaluate concentrations of polybrominated diphenyl ethers (PBDEs), selected alternative flame retardants (AFRs) and total hexabromocyclododecane (HBCDD). The polyurethane foam (PUF) air samplers were deployed in semi-urban, urban and industrial areas and landfill sites in Gauteng Province, South Africa.
The results obtained presented a clear semi-urban–industrial–urban–landfill concentration gradient for all BFRs measured. Taking into account two sampling periods (cold and warm periods) (n = 24), the atmospheric concentrations of Σ9PBDEs (BDE-17, -28, -47, -100, -99, -153, -154, -183, and -209), HBCDDs and ΣAFRs were 80.9 – 1 040 pg·m-3, 29.9 – 71.5 pg·m-3 and 70.9 – 1 990 pg·m-3 in winter and 143 – 2 880 pg·m-3, 11.2 – 142 pg·m-3 and 40.9 – 4 670 pg·m-3 in summer, respectively, for the sparsely populated residential area, densely populated residential area, industrial area and the landfill site. In all cases, BDE-47, BDE-99, and BDE-209 were the predominant PBDE congeners with high detection frequencies. The highest calculated daily exposure dose in Gauteng Province atmosphere was 0.61 and 1.54 ng·kg-1 bw·d-1 for adults and children, respectively. The estimated total intake of PBDEs was 0.47 – 33.4 ng·kg-1 bw·d-1, which was generally below the lowest observed adverse effect level (LOAEL), suggesting that the residents of Gauteng Province may not be significantly affected as a result of their exposure to these pollutants through inhalation. However, this does not necessarily suggest that the pollutants are harmless to human health, since they have the tendency to bioaccumulate in biological systems. Soil samples were also collected and measured, in order to calculate the soil – air exchange relationship. The soil concentrations for Σ9PBDE and ΣAFRs ranged from 8.74– 52.2 ng·g-1 and 9.03 – 61.1 ng·g-1 dry weight (DW) in winter and 4.65 – 22.7 ng·g-1 and 2.69 – 25.7 ng·g-1 DW in summer, respectively. The fugacity fraction (ff) calculations for most compounds were < 0.5 suggesting that the soil in Gauteng Province is more of a sink to PBDEs than a source, and therefore the net deposition happens from the air to the soil. Incidentally, this is the first study from Africa to report on the atmospheric concentrations of PBDEs, HBCDDs and AFRs in urban, landfill and industrial areas. The findings of this study further highlight the contributory role of landfills as potential sources of BFRs in the atmosphere.
Description
Submitted in partial fulfilment of the requirements for the degree, Doctor of Philosophy (PhD) in the Department of Environmental, Water and Earth Sciences
Faculty of Science at the Tshwane University of Technology.
Date
2018-10-20
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Tshwane University of Technology
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Keywords
Chemistry, Tetrabromobisphenol, Polyurethane foam, Organobromine, Gauteng Province, South Africa