The chlorine contents and chain lengths influence the neurobehavioral effects of commercial chlorinated paraffins on zebrafish larvae

Increasing concern has arisen regarding ubiquitous environmental distribution and potential ecological and health risks of chlorinated paraffins (CPs), especially short chain congeners. Four commercial CP products with different carbon chain lengths and chlorine contents were employed to investigate and compare the possible neurotoxic effects on zebrafish larvae at 5 days post fertilization using behavioral tests, including locomotion, path angle, and two-fish social interaction. The high-chlorinated short-chain CP-70 product resulted in the strongest effects in all three tests, while the low-chlorinated long-chain CP-42 product was on the other end of the spectrum. The consequences of the chain length of two CP-52 products could be clearly distinguished by the tests. Although exposure to the two products both caused inhibition in the locomotion test, they resulted in different kinds of effects in the path angle and interaction tests. Our results suggested, as evidenced by the sensitivity and resolution of the behavioral tests, that the influence of the chain length and chlorine content of CPs could be well characterized and that chlorine content consistently showed a more significant impact than chain length. The health threats of long-chain CPs could also not be overlooked when they contained relatively high chlorine contents.