Organic flame retardants in the indoor environment.

Ph. D. University of KwaZulu-Natal, Durban 2014.Flame retardants (FRs) have become ubiquitous contaminants found in humans, animals, various outdoor environments, e.g. air, soil, sediment, etc., and indoor environments particularly, homes, automobiles, classrooms and workplaces all over the world. These chemicals are global contaminants of concern as they are persistent, can bioaccumulate, biomagnify and have potential for long-range atmospheric transport. Most FRs are toxicants to human health since they affect thyroid hormones, endocrine systems and neurobehavioural development and are possibly carcinogenic. The overall hypothesis of this study is that the use of FRs in consumer goods and materials is leading to contamination of indoor environment at levels that may be detrimental to human health. In this study, analytical methods based on gas chromatography-electron impact/mass spectrometry and liquid chromatography electrospray ionization/mass spectrometry were developed and/or validated for the separation, identification and quantitation of various classes of FRs. The FRs investigated included polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), tetrabromobisphenol A (TBBPA) and organophosphate esters [tris(1,3-dichloro-2-propyl) phosphate (TDCPP), tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP) and triphenyl phosphate (TPP)]. These were measured in indoor dust from a wide range of microenvironments, including homes, offices, classrooms, automobiles, three workplaces – an e-waste recycling site, a polyurethane factory and a textile industry – and an in vitro human gastro-intestinal tract (GIT). The measured concentrations of the FRs were used to estimate the exposure of toddlers, teenagers and adults to the FRs of interest via dust ingestion and in some cases dermal absorption of dust by using various exposure scenarios. The relative importance of each exposure route was assessed for the studied population groups. The potential sources of the FRs in the different microenvironments were established by using various advanced parametric and non-parametric statistical tests. Causes of variability in indoor dust concentrations of FRs were elucidated. Two types of in vitro GIT models mimicking the enzymatic and physiochemistry preponderant for a FED and a FASTED state were developed, validated and applied for the first time to study the oral bioaccessibility of organophosphate esters and also to study the bioaccessibility of PBDEs. Strong relationships were found for the bioaccessibility of OPEs and their water solubilities as well as the log Kow of PBDEs

Assessment of human dermal absorption of flame retardant additives in polyethylene and polypropylene microplastics using 3D human skin equivalent models

To overcome ethical and technical challenges impeding the study of human dermal uptake of chemical additives present in microplastics (MPs), we employed 3D human skin equivalent (3D-HSE) models to provide first insights into the dermal bioavailability of polybrominated diphenyl ether (PBDEs) present in MPs; and evaluated different factors influencing human percutaneous absorption of PBDEs under real-life exposure scenario. PBDEs were bioavailable to varying degrees (up to 8 % of the exposure dose) and percutaneous permeation was evident, albeit at low levels (≤0.1 % of the exposure dose). While the polymer type influenced the release of PBDEs from the studied MPs to the skin, the polymer type was less important in driving the percutaneous absorption of PBDEs. The absorbed fraction of PBDEs was strongly correlated (r2 = 0.88) with their water solubility, while the dermal permeation coefficient Papp of PBDEs showed strong association with their molecular weight and logKOW. More sweaty skin resulted in higher bioavailability of PBDEs from dermal contact with MPs than dry skin. Overall, percutaneous absorption of PBDEs upon skin contact with MPs was evident, highlighting, for the first time, the potential significance of the dermal pathway as an important route of human exposure to toxic additive chemicals in MPs

Confirmatory Analysis of Per and Polyfluoroalkyl Substances in Milk and Infant Formula Using UHPLC–MS/MS

An ultra-high performance liquid chromatography tandem mass spectrometry method was developed and validated for the sensitive determination and unambiguous confirmation of residues of per and polyfluorinated alkyl substances (PFAS) in breastmilk, retail milk and infant formulas following two sample preparation methods. Sample pre-treatment was carried out by a simplified QuEChERS method without requiring dSPE or any further clean-up. The method was validated in accordance with the requirements of Commission Decision 657/2002/EC with slight modifications. The method displayed good linearity with R(2) ranging from 0.9843–0.9998 for all target PFAS. The recovery and within-laboratory reproducibility of the method (n = 63) were in the range 60–121% and 5–28%, respectively. The decision limit, detection capability and limit of quantitation ranged from 30–60 ng kg(−1) to 40–100 ng kg(−1) and 5–50 ng kg(−1), respectively. Acceptable matrix effect values in the range −45–29% were obtained with uncertainty of measurement lower than 25% for all target PFAS. The method displays its suitability for the sensitive and high-throughput confirmatory analysis of C(4)–C(14) PFAS in breastmilk, dairy milk and infant formulas