Toxicological Analysis of PAH-rich Soot Extracts from PUV Exhausts Using the Zebrafish Embryo Assay

Abstract

Background & Objective: Polycyclic aromatic hydrocarbons (PAH) are among the most toxic environmental pollutants and carcinogens known. Vehicular emissions resulting from rampant utilization of fossil fuel and other petrogenic resources have increased PAH levels in the environment. Renewed interests among scientists have emerged to determine the ecotoxicological potencies of PAH-rich soots derived from incomplete combustion of fuels used by the transport sector. Thus, the present study was carried out to investigate the kinds, concentrations, and embryotoxicity potential of the two categories of PAH-laden soot extracts obtained from public utility vehicle (PUV) tailpipes.

Methodology: Two categories of soot from pure diesel and diesel-biodiesel blend-fuelled vehicles, were collected from tailpipes of public utility vehicles (PUVs) stationed in several terminals along Quezon City,
Philippines. All samples were subjected to solid-phase extraction clean-up, followed by GC/MS spectrometric analyses to determine the kinds and concentrations of PAHs. The soot extracts were also prepared and used for the zebrafish embryo assay.

Results & Conclusions: Results showed that both types of soot samples contained comparable levels of environmentally relevant PAHs. The diesel extracts contained 10 PAHs that registered higher average levels compared to only 4 in the fuel blend extracts. All undiluted extracts, whether from diesel or fuel blend soot, were embryotoxic to zebrafish embryos (ie., egg coagulation within 12 to 24 hrs). Extracts from both types of soot showed decreasing levels of toxicities upon dilution, in terms of the number of abnormalities and lethal endpoints observed. Overall, there was no marked difference between the two types of soot extracts in terms of toxicities and PAH kinds and levels. The results of the study could provide a benchmark for the development of a rapid-response model for predicting teratogenic potential of combustion-derived soots in a broad range of vertebrates.