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Darwin R. Reyes,^1,2 Osvaldo Rosario,² Jose F. Rodriguez,^1,3 and Braulio D. Jimenez^1,3

¹Center for Environmental and Toxicological Research, School of Medicine, Medical Sciences Campus, University of Puerto Rico, San Juan, Puerto Rico; ²Department of Chemistry, Rio Piedras Campus, University of Puerto Rico, San Juan, Puerto Rico; ³Department of Biochemistry, School of Medicine, Medical Sciences Campus, San Juan, Puerto Rico

Abstract

In recent years, several hypotheses have emerged to explain the toxicologic activity of particulate matter. Organic compounds, ultrafine particles, biologic components, and transition metals are some of the constituents that reportedly exert some type of adverse effect on human health. A considerable fraction of the urban particulate matter consists of carbon compounds, which originate mostly from anthropogenic sources. The toxicity of organic fractions from particulate matter have been mainly evaluated by considering their mutagenic activity. This research expands on the toxicologic profile of organic compounds adsorbed to particulate matter, specifically in Puerto Rico, by using the cytotoxic neutral red bioassay (NRB) . The NRB uses normal human epidermal keratinocytes or other types of cells to measure the effect on cell viability when exposed to organic compounds associated to the particles in the air. We validated the NRB for particulate matter by using a standard reference material (SRM 1649) . We used the NRB to determine toxicologic differences of extracts between an urban industrialized site with anthropogenic activity versus a coastal region with less human activity. The cytotoxicity associated with organic compounds in particulate matter collected at the urban industrialized site was detected in both the particulate matter 10 µm in aerodynamic diameter (PM₁₀) and particulate matter 100 µm in aerodynamic diameter (PM₁₀₀) . Greater toxic effects were observed in PM₁₀ extracts than in PM₁₀₀ extracts, but PM₁₀ toxic effects were not significantly different from those in PM₁₀₀. The extracts from the industrialized site were more cytotoxic than the extracts from coastal reference site, although in the summer, extracts from both sites were significantly cytotoxic to normal human epidermal keratinocytes. In addition, the nonpolar extracts of both PM₁₀ and PM₁₀₀ exerted the greatest cytotoxicity, followed by the polar, and, finally, the moderately polar extract. This study demonstrates that extracts from the Guaynabo industrialized site were more toxic than similar extracts obtained from a reference coastal site in Fajardo, Puerto Rico. Key words: air pollution, bioassay, cytotoxicity, human cells, organic extracts, particulate matter, PM₁₀, PM₁₀₀, SRM 1649, toxicity. Environ Health Perspect 108:635-640 (2000) . [Online 1 June 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p635-640reyes/ abstract.html

Address correspondence to B.D. Jiménez, Center for Environmental and Toxicological Research, University of Puerto Rico, Medical Sciences Campus, PO Box 365067, San Juan, PR 00936-5067 USA. Telephone: (787) 758-2525 ext 1235. Fax: (787) 753-8784. E-mail address: b_jimenez@rcmaca.upr.clu.edu

We thank R. Delgado for technical assistance, the Puerto Rico Environmental Quality Board (particularly A. Morales) for providing filter samples, and the Conservation Trust of Puerto Rico for allowing the location of the samplers in a protected area.

This work was supported by EPA-EPSCoR (R821843-01-0) and RCMI (RR-03051) . D.R.R. acknowledges the pre-doctoral fellowship provided by the NASA-EPSCoR Program (NGT40053) .

Received 11 August 1999 ; accepted 7 March 2000.