Comparative toxicological analysis of polycyclic aromatic hydrocarbon (PAH)-rich soot extracts from gasoline and LPG-fueled taxis using the Zebrafish Embryo Toxicity (ZFET) test.

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous compounds which are known to be teratogenic and embryotoxic. Many fuel sources, such as liquefied petroleum gas, are currently examined as alternatives to gasoline use in automobiles to help reduce environmental pollutants, such as PAHs. In the Philippines, LPG is the most widely used alternative fuel source due to its lower market price. In this study, a comparison of the kinds, concentrations, and toxicological potencies of PAHs from soot extracts obtained from LPG-powered and gasoline-powered taxi tailpipes was conducted using GC-MS analysis and the zebrafish embryotoxicity (ZFET) test. GC-MS results showed that both liquefied petroleum gas (LPG) and unleaded gasoline (UG) extracts contain comparable levels of environmentally relevant PAHs. Unleaded gasoline extracts contained 7 PAHs, compared to only 4 identified in LPG extracts. However, the total PAH concentration of PAHs found in LPG extracts was higher than what was detected in UG extracts. Dilutions ranging from 1:0 (undiluted) to 1:4 were embryotoxic to zebrafish embryos. A dose response relationship was seen in both types of soot extracts with decreasing mortalities and developmental abnormalities observed upon dilution from 1:5 to 1:25, with zebrafish embryos exhibiting lethal and sublethal endpoints. Moreover, the embryotoxic responses of zebrafish upon exposure to LPG and UG soot extracts were statistically comparable. Given these results debunk the claim that LPG is a cleaner and safer‘ fuel source, further investigations on the toxicological potencies of other alternative fuel sources should be performed to determine which fuel source should be used to help reduce PAHs in the environment. Moreover, it would be helpful in the development of policies on the use of alternative fuels to help reduce PAH levels in the country.