Polybrominated diphenyl ethers and the multi-element profile of house dust in Croatia: Indoor sources, influencing factors of their accumulation and health risk assessment for humans
Graphical abstract
Introduction
Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs), manufactured and added to fabrics, furnishings, electronics and vehicles to prevent fire outbreak or reduce the flame spread and consequent human and material fire damages. Three commercial mixtures were used: pentaBDE (commercially known as DE-71 and Bromkal 70-5DE), composed mainly of BDE-47, -99, -85, -100, -153, and -154, with the first two congeners as major components; octaBDE (DE-79), composed of BDE-153, -154, -183, -196, -197, -203, -206 and -207 with BDE-183 as major component; and decaBDE (DE-83R or Saytex 102E), essentially composed of BDE-209 (La Guardia et al., 2006).
Main applications differ between mixtures, so pentaBDE was mainly used as an additive e.g. for polyurethane foams - used in furniture industry, production of insulating materials and for textiles (carpets, curtains, decorative pillows). Mixtures of octaBDE and decaBDE have been used mainly as additives to epoxy resins, polyamide fibers, polyethylene, and polystyrene in the manufacturing of housing components for electrical and electronic equipment (U.S. EPA, 2010).
In the light of growing evidence regarding their persistence, omnipresence, and toxicity, the production of pentaBDE and octaBDE mixtures was discontinued in Europe and United States in 2004. Four years later, the application of decaBDE mixtures in electric and electronic devices was phased out in Europe, and in 2013 their use was completely banned in the United States. However, due to their continuous release into the environment from products that remain in use or from various dump sites and recycling facilities, these compounds are likely to be present in the environment for many years to come (Kalachova et al., 2012; Zota et al., 2008). Epidemiological studies indicate a connection between PBDE exposure and lower birth weight, changes in thyroid hormone levels, and impaired cognitive, motor, and neurobehavioral development (Drobná et al., 2019; Gibson et al., 2018).
Similar to PBDEs, trace elements are ubiquitous in nature and extensively detected in the environment, households and workplaces. Because of their toxicity, some metal compounds present a major threat to the public health even at low levels of exposure. This is particularly evident with elements that in the case of long-term exposure tend to accumulate in the human body over lifetime. Although each element exhibits its unique toxicology, their common mechanisms of toxicity include mimicry, adduct formation with DNA or protein, and oxidative damage, resulting in immunotoxicity, reproductive toxicity, and endocrine disruption with endpoints related to cancer induction (Beyersmann and Hartwig, 2008; Silvera and Rohan, 2007; Tariba Lovaković et al., 2021).
Dust is a heterogeneous mixture of particulate matter and acts as a sink for a wide variety of contaminants (Chakraborty et al., 2016). Due to the large specific surface area and high organic content, dust acts as a good repository, as well as a transport medium for both, flame retardants and trace elements (Ali et al., 2012; Doyi et al., 2019; Jadoon et al., 2021). Still, along to different dust sampling approaches (vacuum-cleaner bags vs. dust collected by researchers; floor vs. elevated surfaces dust), substantial within- and between-room spatial variation, as well as possible temporal variability can affect dust contaminant levels, and consequently human exposure estimates. House dust particles containing PBDEs/trace elements can be generated indoors from materials used in building construction and interior decoration (furnishing, carpets, curtains), emissions from heating systems, living habits of residents (e.g. cigarette smoking) or carried inside from soil/street dust and/or outdoor air containing suspended particulate matter from anthropogenic activities (industrialization, vehicular traffic, urbanization) (Ibanez et al., 2010). As a consequence of today's indoor lifestyle (according to Klepeis et al. (2001) people spend more than 90% of their time indoors), combined exposure to compounds accumulated in indoor dust becomes an important factor that can have negative consequences for human health.
In general, diet is considered as the main intake route for both elements and organic contaminants. In the case of PBDEs, indoor dust was found to play an important role in PBDE body burdens in addition to food (Schecter et al., 2006). Exposure to compounds contained in dust can occur via inhalation, ingestion or skin contact, and some routes of exposure dominate depending on the properties of an individual compound or group of compounds. According to recent detailed surveys (Bu et al., 2020; Wu et al., 2020) intake via dust ingestion was proved to be the most dominant pathway of exposure to PBDEs compared to inhalation of air/dust particles or dermal absorption. In addition, numerous studies confirmed that toddlers exhibit higher exposure to contaminants such as PBDEs and trace elements due to their close-to-ground behavior, hand-to-mouth contact, and consequently higher dust intake rates (Doyi et al., 2019; Glorennec et al., 2012). Precisely because of higher exposure, children are the most vulnerable population group for adverse health effects that PBDEs and toxic elements may induce.
Risk assessments of exposure to PBDEs and toxic elements from soils and dust have been conducted in occupationally exposed population working at e-waste or plastic waste recycling sites (Akortia et al., 2017; He et al., 2017; Ohajinwa et al., 2019; Tang et al., 2016; Xu et al., 2015). Although the reported results are inconsistent, these studies agree on one issue – there is cause for concern regarding exposure to PBDEs/trace elements, especially for toddlers. Most studies reported that some toxic elements (Pb, Sb) exceed acceptable risk levels, while the health risk of exposure to PBDEs from dust is generally low (Akortia et al., 2017; Tang et al., 2016; Xu et al., 2015). On the other hand, He et al. (2017) calculated that estimated daily intake (EDI) of BDE-209, Cd and Pb in toddlers in the e-waste recycling area in South China exceeds the reference dose, indicating the high exposure risk of these pollutants. In addition, Ohajinwa et al. (2019) found that cumulative health risks from combined exposure to PBDEs and trace elements at informal electronic waste recycling sites in Nigeria exceeds the acceptable limits of both non-cancer effects and cancer risk.
Despite extensive information regarding indoor dust levels of PBDEs and trace elements in Europe, North America, and China there is little or no information regarding their concentrations in indoor dust in some areas of the world including Croatia (except for our recent preliminary investigation report on PBDEs in dust by Jagic et al. (2021)). Moreover, most investigations on levels of trace elements in household dust focus on locations near sources of pollution. To the best of our knowledge, there are no available data on cancer risks and non-cancer hazards of concurrent exposure to PBDEs and trace elements found in house dust of non-occupationally exposed residents or those not living near polluting industries.
In this regard, the main objectives of the current study were to: 1) determine the levels and profiles of 7 PBDE congeners and 18 elements in household dust from Zagreb; 2) explore possible source of detected contaminants on the basis of the relationship between their concentrations, house characteristics and the habits of the residents; 3) estimate PBDEs/elements exposure rates of adults and toddlers through ingestion and dermal absorption of house dust at central and worst case scenarios; 4) assess whether either of the two age groups are at health risk due to exposure to PBDEs/elements in dust.
Section snippets
Target compounds
Samples were analyzed for 7 PBDEs (2,4,4′-tribromodiphenyl ether (BDE-28), 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), 2,2′,4,4′,5-pentabromodiphenyl ether (BDE-99), 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100), 2,2′,4,4′,5,5′-hexabromodiphenyl ether (BDE-153), 2,2′,4,4′,5,6′-hexabromodiphenyl ether (BDE-154), and 2,2′,3,4,4′,5′,6-heptabromodiphenyl ether (BDE-183)) and 18 elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, Tl, V, and Zn).
Sample collection
Dust samples (N = 68) were
PBDE concentrations and congener profile
BDE-28 was the only congener not detected in any of the dust samples, which was probably due to its higher volatility and reduced tendency to remain in the dust. The most frequently detected congeners were BDE-99 and BDE-183, measured in 94% and 88% of samples, respectively. The remaining congeners were detected with frequency between 28% for BDE-154 and 72% for BDE-153.
Mass concentrations of ΣPBDE ranged from 0.16 and 200.09 ng g−1 dust, but more than 62% (n = 42) of dust samples contained the
Conclusion
Given the large proportion of time that people nowadays spend indoors, biomonitoring and evaluation of the potential health risks posed by various contaminants in the indoor environment is of great importance. This is the first study to present PBDE and multi-element profile of house dust collected from Croatian households. Concentrations of detected PBDE congeners and trace elements in our study were mostly similar or lower than the ones reported elsewhere. In areas such as Zagreb, with no
CRediT authorship contribution statement
Darija Klinčić: Conceptualization, Visualization, Writing – original draft, Resources, Supervision, Funding acquisition. Blanka Tariba Lovaković: Investigation, Visualization, Conceptualization, Writing – original draft. Karla Jagić: Methodology, Validation, Investigation, Writing – review & editing. Marija Dvoršćak: Validation, Visualization, Conceptualization, Writing – review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported in part by the Croatian Science Foundation under project HrZZ-UIP-2017-05-6713. The authors express their thanks to all the dust donors for their willingness to participate in the study as well as to Nikolina Medved for technical assistance.
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