Toxicity of polycyclic aromatic hydrocarbons to the nematode caenorhabditis elegans

The presence of polycyclic aromatic hydrocarbons (PAHs) in the environment has attracted much concern owing to their mutagenic and carcinogenic properties. Regulatory authorities have favored the use of biological indicators as an essential means of assessing potential toxicity of environmental pollutants. This study aimed to assess the toxicity of acenaphthene, phenanthrene, anthracene, fluoranthene, pyrene, and benzo[a]pyrene to Caenorhabditis elegans by measuring LC50 and EC50 values for growth and reproduction. The exposure to all chemicals was carried out in aqueous medium. All PAHs showed a low acute toxicity to C. elegans. There was no significant mortality in C. elegans after 24 h of exposure at PAH concentrations within (and indeed above) their respective solubility limits. Prolonged exposure (72 h) at high concentrations for acenaphthene (70,573 µg/L), phenanthrene (3758 µg/L), anthracene (1600 µg/L), fluoranthene (1955 µg/L), pyrene (1653 µg/L), and benzo[a]pyrene (80 µg/L) produced mortality. Results also showed that reproduction and growth were much more sensitive parameters of adverse response than lethality, and consequently may be more useful in assessing PAH toxicity using C. elegans. In comparison with previous studies, C. elegans was found to be approximately 2-fold less sensitive to acenaphthene, 5-fold less sensitive to phenanthrene, and 20-fold less sensitive to fluoranthene than Daphnia magna. However, the 48-h LC50 for benzo[a]pyrene (174 µg/L) reported in the present study with C. elegans was similar to that reported elsewhere for Daphnia magna (200 µg/L). Although C. elegans indicated greater sensitivity to benzo[a]pyrene than Artemia salina (174 µg/L vs. 10000 µg/L), the organism showed less sensitivity to pyrene (8 µg/L vs. 2418 µg/L), fluoranthene (40 µg/L vs. 2719 µg/L), and phenanthrene (677 µg/L vs. 4772 µg/L) than Artemia salina. Caenorhabditis elegans, while not the most sensitive of species for PAH toxicity assessment, may still hold applicability in screening of contaminated soils and sediments.