Human dermal absorption of chlorinated organophosphate flame retardants; implications for human exposure

Abstract

Tris-2-chloroethyl phosphate (TCEP), tris (1-chloro-2-propyl) phosphate (TCIPP) and tris-1,3-dichloropropyl phosphate (TDCIPP) are organophosphate flame retardants (PFRs) widely applied in a plethora of consumer products despite their carcinogenic potential. Human dermal absorption of these PFRs is investigated for the first time using human ex vivo skin and EPISKIN™ models. Results of human ex vivo skin experiments revealed 28%, 25% and 13% absorption of the applied dose (500 ng/cm(2), finite dose) of TCEP, TCIPP and TDCIPP, respectively after 24h exposure. The EPISKIN™ model showed enhanced permeability values (i.e. weaker barrier), that were respectively 16%, 11% and 9% for TCEP, TCIPP and TDCIPP compared to human ex vivo skin. However, this difference was not significant (P>0.05). Estimated permeability constants (Kp, cm/h) showed a significant negative correlation with log Kow for the studied contaminants. The effect of hand-washing on dermal absorption of PFRs was investigated. Washing reduced overall dermal absorption, albeit to varying degrees depending on the physicochemical properties of the target PFRs. Moreover, slight variations of the absorbed dose were observed upon changing the dosing solution from acetone to 20% Tween 80 in water, indicating the potential influence of the dose vehicle on the dermal absorption of PFRs. Finally, estimated dermal uptake of the studied PFRs via contact with indoor dust was higher in UK toddlers (median ΣPFRs=36 ng/kg bw day) than adults (median ΣPFRs=4 ng/kg bw day). More research is required to fully elucidate the toxicological implications of such exposure.

Health hazard evaluation report: evaluation of occupational exposure to flame retardants at four gymnastics studios.

“…Other reasons include the possibility that aspects of washing other than frequency, i.e., vigor and duration, may be important or we may not have had enough people throughout the frequency range to see a correlation. Other studies have shown an inverse association between frequency of handwashing and concentrations of some flame retardants on hands [Abdallah et al 2016;Stapleton et al 2014;Watkins et al 2011].…”

“…Experimental data using human skin equivalent tissue demonstrates that absorption through skin increased as the number of bromine atoms decreased for PBDEs [Abdallah et al 2015]. Animal studies show that TDCPP is easily absorbed through the skin and gastrointestinal tract [Nomeir et al 1981], and recent studies of human ex vivo skin showed absorption of 28% for TCEP, 25% for TDPP, and 13% for TDCPP [Abdallah et al 2016]. Neither NIOSH, OSHA, nor the American Conference of Governmental Industrial Hygienists has limits for flame retardants on hands or surfaces.…”

Evaluation of exposure to metals, flame retardants, and nanomaterials at an electronics recycling company.

“…Office workers who washed their hands fewer than four times daily had significantly higher levels of PentaBDE on their hand wipes than those who washed four or more times daily [Watkins et al 2011]. Absorption of TCIPP and TCEP was significantly reduced by hand washing in an experimental study using human ex vivo skin, but penetration continued, presumably from the reservoir in the skin [Abdallah et al 2016]. Hand washing did not significantly reduce absorption of TDCIPP [Abdallah et al 2016].…”

“…Absorption of TCIPP and TCEP was significantly reduced by hand washing in an experimental study using human ex vivo skin, but penetration continued, presumably from the reservoir in the skin [Abdallah et al 2016]. Hand washing did not significantly reduce absorption of TDCIPP [Abdallah et al 2016]. …”

“…Experimental data using human skin equivalent tissue demonstrates that absorption through skin increased as the number of bromine atoms decreased for PBDEs [Abdallah et al 2015]. Animal studies show that TDCIPP is easily absorbed through the skin and gastrointestinal tract [Nomeir et al 1981], and recent studies of human ex vivo skin showed absorption of 28% for TCEP, 25% for TCIPP, and 13% for TDCIPP [Abdallah et al 2016].…”