US and Canadian research teams are calling for research into possible health effects of a "novel" organophosphate ester (OPE) found in house dust: tris(2,4-di-tert-butylphenol)phosphate (TDTBPP).
One team "stumbled" upon the chemical during routine screening for flame retardants, according to lead author Marta Venier, from Indiana University, US.
Meanwhile, in August, Runzeng Liu and Scott Mabury from the University of Toronto, Canada, reported "unexpectedly high concentrations of a newly identified" OPE in household dust. The researchers found TDTBPP in all office and house dust samples collected in Toronto, suggesting that "human OPE exposures in indoor environments is greater than was previously reported".
TDTBPP is known to form from a plastic additive called tris(2,4-di-tert-butylphenol)phosphite, which is widely used to stop polymers degrading during high temperature extrusion, sterilisation (food packaging), and storage. While protecting against oxidation, the chemical is itself oxidised to TDTBPP.
An OECD report suggests that around 46% of the phosphite oxidises to TDTBPP during polymer processing. The Toronto team detected the phosphite antioxidant in 50% of dust samples.
'Cause for concern'
But Dr Venier suspects that TDTBPP itself may be used as a flame retardant, based on the fact that the researchers first found high concentration in electronic waste dust.
Further investigations revealed that the chemical was in "pretty much every sample that we looked for," from house dust to canal sediment in the Great Lakes region, she added. "This, joined with the fact that we don't know anything about its toxicity, is for us a cause for concern and it speaks of poor chemical management," she told Chemical Watch.
The researchers will continue to monitor for the compounds in other samples. They will also modify their analytical techniques to clarify if the TDTBPP results mainly from phosphite oxidation or whether it is indeed being used as a standalone additive.
Although there is a fair amount of literature on the phosphite, both teams point to a lack of toxicity information for TDTBPP. "The elevated concentrations measured in the built and natural environment, and the relatively high exposure estimates, especially for toddlers, indicate that further investigation of this compound and the related TDTBPPO [tris(2,4-di-tert-butylphenol)phosphite] is warranted," wrote Dr Venier and colleagues in the journal Environmental Science and Technology.
Dr Liu and Professor Mabury also called for more studies to evaluate potential toxicity and to find out if more OPE analogues are present in the environment "to avoid underestimating human exposure". As they point out, human dust exposure is "unavoidable".
The Toronto team is not currently investigating TDTBPP's potential toxicity but urged others to take on the work. "We will be happy if someone else would like to investigate its toxicity as this chemical was detected at high concentrations of parts-per-million levels in various environmental samples, which leads to ubiquitous human exposure," said Dr Liu.