TIP sponsored an in vivo inhalation hazard assessment to improve scientific understanding of any hazard associated with potential human exposure to airborne TRWP. This research did not produce any adverse effects at tested concentrations.
An understanding of the potential for human exposure to airborne TRWP has been achieved through a TIP sponsored exposure assessment. TIP developed a chemical marker to distinguish TRWP from other roadway-sourced airborne particulate matter (PM), such as brake wear and vehicle exhaust emissions.
Using the marker, the TIP sponsored exposure assessment detected TRWP in soil, sediment, and as airborne PM.
TRWP was found in the highest concentrations in soil, at the closest proximity to the road, decreasing in concentration as the distance from the road increased.
In air, TRWP were found to make only a minor contribution to the total of particulate matter collected in the PM10 and PM2.5 range. PM10 and PM2.5 are PM that have diameters of less than 10 and 2.5 micrometers respectively. These are size fractions that can become airborne, and particles of less than PM10 are interesting for human health risk assessment as they can be inhaled.
A risk assessment that considered the potential for exposure to airborne TRWP and the potential hazard associated with TRWP in the PM10 and PM2.5 size ranges concluded that there is unlikely to be a risk to humans from exposure to TRWP in the air.