World Trade Center Fine Particulate Matter Causes Respiratory Tract Hyperresponsiveness in Mice.

Pollutants originating from the destruction of the World Trade Center (WTC) in New York City on 11 September 2001 have been reported to cause adverse respiratory responses in rescue workers and nearby residents. We examined whether WTC-derived fine particulate matter [particulate matter with a mass median aerodynamic diameter < 2.5 µm (PM[sub 2.5])] has detrimental respiratory effects in mice to contribute to the risk assessment of WTC-derived pollutants. Samples of WTC PM[sub 2.5] were derived from settled dust collected at several locations around Ground Zero on 12 and 13 September 2001. Aspirated samples of WTC PM[sub 2.5] induced mild to moderate degrees of pulmonary inflammation 1 day after exposure but only at a relatively high dose (100 µg). This response was not as great as that caused by 100 µg PM[sub 2.5] derived from residual oil fly ash (ROFA) or Washington, DC, ambient air PM [National Institute of Standards and Technology, Standard Reference Material (SRM) 1649a]. However, this same dose of WTC PM[sub 2.5] caused airway hyperresponsiveness to methacholine aerosol comparable to that from SRM 1649a and to a greater degree than that from ROFA. Mice exposed to lower doses by aspiration or inhalation exposure did not develop significant inflammation or hyperresponsiveness. These results show that exposure to high levels of VWFC PM[sub 2.5] can promote mechanisms of airflow obstruction in mice. Airborne concentrations of WTC PM[sub 2.5] that would cause comparable doses in people are high (∼ 425 µg/m³ for 8 hr) but conceivable in the aftermath of the collapse of the towers when rescue and salvage efforts were in effect. We conclude that a high-level exposure to WTC PM[sub 2.5] could cause pulmonary inflammation and airway hyperresponsiveness in people. The effects of chronic exposures to lower levels of WTC PM[sub 2.5], the persistence of any respiratory effects, and the effects of coarser WTC PM are unknown and were not... [ABSTRACT FROM AUTHOR]