Evaluation of polycyclic aromatic hydrocarbons in silky sharks Carcharhinus falciformis collected from Western Indian Ocean and human health risk assessment

The silky shark (Carcharhinus falciformis) is the most abundant and widely distributed shark species in the marine system of tropical regions. However, it appears that there is limited information on USEPA 16 polycyclic aromatic hydrocarbons (PAHs) concentration in silky shark muscle tissue, which has together with the lack of a health risk assessment of human consumption of silky shark filets. The potential toxicity of PAHs in muscles of silky sharks and cancer and non-cancer risk of consumers were assessed. Results showed that the total PAHs (TPAHs) concentration in the muscle tissue of silky sharks was between 62 and 657 ng/g ww, with an average of 234 +/- 221 (mean +/- standard deviation) ng/g ww, and can be considered as minimally to moderately contaminated level. Naphthalene (NA), phenanthrene (PH), and fluoranthene (FLU) are the most abundant PAHs in silky sharks muscle tissue, accounting for 38.6%, 11.0%, and 19.0% of TPAHs, respectively. The average values of toxic benzo[a]pyrene (BaP) equivalent (TEQ(carc)) and toxic dioxin equivalent (TEQ(fish)) of PAHs equal to the potency of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in silky shark muscle are 13.5 +/- 16.4 ng BaP/g ww and 34.1 +/- 77.4 pg TCDD/g ww, respectively, and they showed a good linear relationship (r = 0.928; p < 0.001). The TEQ(carc) of silky sharks muscle is higher than USEPA's screening value of PAHs of 3.2 ng BaP/g ww for adults, indicating a potential negative impact on public health. The calculated hazard index (HI) of PAHs is less than 1, suggesting that residents eating silky shark muscle will not expect to cause significant non-cancer risk. However, the incremental lifetime cancer risk (ILCR) of BaP as 10.6-26.3 % and 8.2-32.4% in males and females, respectively, may pose a significant cancer risk. In general, children and the elderly have relatively higher risks, as well as males have a higher cancer and non-cancer risk than females.