Toward understanding of the magnitude and pathways of human dietary exposure to organophosphate esters (OPEs)

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Gbadamosi, Muideen R. ORCID: https://orcid.org/0000-0002-9069-4688 (2023). Toward understanding of the magnitude and pathways of human dietary exposure to organophosphate esters (OPEs). University of Birmingham. Ph.D.

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Abstract

Organophosphate esters (OPEs) are flame retardant and plasticizer used as a substitute for brominated flame retardants (BFRs) and are added to electronics, furniture, textiles, and other consumer products. The ubiquitous presence of OPEs in various environmental matrices and their suspected adverse effects worldwide has become a major concern. Numerous studies have indicated that components of OPEs have several significant biological effects including, neurotoxicity, kidney toxicity carcinogenicity and reproductive toxicity. Findings from our previous review has established that food is an important and the main human exposure pathway to OPEs and evaluated the relative significant of dietary exposure in comparison with other human exposure pathways such as air inhalation, dust ingestion, water ingestion and infant exposure through breast milk. While inhalation exposure and especially exposure via indoor dust ingestion are relatively well-characterised, exposure via the diet and drinking water were highlighted as potentially important omissions. Furthermore, a dearth of data for Africa was highlighted. Therefore, the purpose of this thesis is to evaluate the occurrence, fate, and magnitude of dietary exposure to eight (8) OPEs in UK foodstuffs and UK drinking water and foodstuffs from African origin, estimate the magnitude of human exposure risk in indoor dust from Nigeria and sediment samples from major Rivers in Southwest Nigeria.
The chapter one and two of this thesis entails a detailed introduction and published critical review on human exposure to OPEs with a focus on dietary intake. Chapter three contained the description of analytical method and first comprehensive study to determine the concentrations of eight OPEs in UK foodstuffs and evaluate the exposure risk for all age groups using GC-MS. In UK foodstuffs, the concentrations of the∑8OPEs were highest (mean ∑8OPEs = 18.4 ng/g wet weight (ww)) in milk and milk products, followed by those in cereal and cereal products (mean ∑8OPEs = 15.9 ng/g ww), with concentrations lowest in chickens’ eggs (mean ∑8OPEs = 1.61 ng/g ww). Chapter four of this thesis determined the significance of water ingestion as a pathway of human exposure to OPEs in UK population. Our results showed that water ingestion (most especially tap water) was a significant source of chlorinated OPEs (TCEP and TCIPP) and alkyl-OPEs (TBOEP) and aryl-OPEs (TPHP and EHDPP). Based on the developed method, in Chapter five we investigated the concentrations of the 8 OPEs in indoor dust from homes, car/bus, office and medical centres from Nigeria to investigate the concentrations and profiles of target OPEs in indoor dust from Nigeria, (ii) compare the concentrations profiles of OPEs in the different microenvironment (cars, offices, medical centres, and residential homes) (iii) to identify and apportion the possible sources of the OPEs in the indoor dust from the selected microenvironment in Nigeria (iv) to estimates the magnitude of human exposure risks to OPEs via indoor dust ingestion in Nigeria. Our results showed that OPEs concentrations from the indoor dust were among the lowest reported from other countries. This may be ascribed to less strict fire safety standard and lack of regulatory actions against brominated flame retardants. There are no significant differences (p ˃ 0.05) between the ∑8OPEs mean concentrations found in dust samples from car/bus (295 ng/g), offices (231 ng/g), residential homes (277 ng/g) and medical centres (127 ng/g). Then finally, in Chapter six, determined the level, distribution and dietary exposure assessment of the OPEs in a wide range of foodstuffs of Nigeria origin. Our findings in chapter three and six further established that food processing and packaging materials is an important potential food contamination source. To the best of our knowledge, findings from all the chapters represents the first comprehensive studies for the target OPEs in UK and Nigeria and first survey of OPEs presence in foodstuffs from African origin.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):