Organophosphorus flame retardants
The appearing toxicity and persistence of the brominated flame retardants (BFRs), such as the polybrominated diphenylethers (PBDEs), led to the ban or restriction of their use. The continuous need for ways to decrease flammability of products resulted in increased use of alternative flame retardants, such as organophosphorus flame retardants (OPFRs). OPFRs are additive flame retardants, meaning that they are not chemically bonded to treated materials and can leave the products. The common feature of the OPFRs is the organophosphorus entity with three substitutions attached to it, often but not always, with the same structure (Figure 1).
Figure 1. Structures of the chemicals analyzed in the dust samples
OPFRs are also used as plasticizers and stabilizers in various products, such as building materials, electronics and furnishing materials. Given that OPFRs are incorporated in such a variety of materials and products, sampling of dust provide a good matrix to assess the overall exposure of OPFRs in the indoor environment.
The total concentration of OPFRs ranged from 11 to 32 µg/g dust in the individual houses (Dahlberg and Weiss 2016). The composition of individual OPFR differed between samples and is likely reflecting the different building materials, furniture and consumer products present in the represented homes. TBOEP and TCIPP were found in highest concentrations (20 and 19 µg/g dust, respectively). TBOEP is used in floor polishes and as a plasticizer in rubber and plastics whereas TCIPP is used in rigid and flexible polyurethane foams used in for example furniture upholstery.
Figure 2. The individual OPFRs analysed in dust from the living rooms of the 17 households participating in the project. Home 6 was sampled twice, with one year in between. Home 12, 14 and 16 contained pooled dust from the living room and adults bedroom.
The OPFRs was not analyzed in the cat serum, although possible. These compounds are rapidly excreted with the urine and urine is very difficult to sample from cats. Recently though, a study successfully analysed and published serum levels of OPFRs in cats, from the Canary Islands for the first time (Henriques-Hernandez et al. 2017). In that study, blood serum from the cat owners were also analyzed and the levels of OPFRs were comparable (sum OPFRs in cats was 910 ng/g fat and humans 880 ng/g fat). In the same samples, the PCBs and PBDEs were also analyzed and the OPFR levels were 200 times higher than the PBDE levels and 2500 times higher than the PCBs levels in serum, reflecting the high concentrations these chemicals are used in our products. That study did not analyze the dust from the participating families homes, so comparisons to this study is difficult to make. One study analysed OPFRs in dust from homes in Belgium and reported average concentration of the sum of OPFRs to be 19 ug/g dust, i.e. very similar to our study (Van den Eede et al. 2011). TBOEP dominated the profile also in that study, with concentrations ranging 0,4-68 µg/g dust.
Another study in the USA studied the possible effect these compounds could have on human health. They analyzed house dust from 50 men recruited through a U.S. infertility clinic for TDCPP and TPP to measure the relationships with reproductive and thyroid hormone levels, as well as semen quality parameters (Meeker and Stapleton 2010). The average TDCPP and TPP levels were 1.9 and 7.8 mg/g dust, respectively, and all up to 1.8 mg/g for TPP in one house dust was measured. That is 1000 times higher than found in European dust. The study showed that increasing levels of TDCPP in dust was associated with a decline in free thyroxine (3%) and an increase in prolactin (17%) in the mens serum. Also, and increase in TPP dust levels was associated with an increase in prolactin (10%) and a decrease in sperm concentration (19%).
It is difficult to draw any solid conclusions regarding the risk with the current exposure to these compounds, despite indications that they might influence a normal body function. What is most unsettling is the prevalence of these compounds in every single household. The profiles show that it is difficult to avoid these chemicals, which are considered as high production volume chemicals (HPVC). HPVC are defined as being produced at levels greater than 1,000 metric tons per producer/importer per year in at least one member country/region (OECD and EU) and undergo a more rigid toxicity testing than lower volume chemicals. EU is currently looking into how to better evaluate the chemicals endocrine disrupting potency, which today is one of the most urgent concerns within risk assessments.
- Dahlberg, A.K. and Weiss, J.M. (2016). Organophosphorus flame retardants in Swedish house dust. Organohalogen Compounds 78: 1174-1177
- Meeker, J.D. and Stapleton, H.M. (2010). House dust concentrations of organophosphate flame retardants in relation to homrone levels and semen quality parameters. Environ. Health Perspect. 118(3): 318-323
- Henríquez-Hernánde et al. (2017). Potential role of Pet cats as a sentinel species for human exposure to Flame retardants. Front. Vet. Sci 4:79
- Van den Eede et al. (2011). Analytical developments and preliminary assessment of human exposure to organophosphate flame retardants from indoor dust. Environ. Int. 37: 454-461.