Interaction of perfluoroalkyl sulfonates with caenorhabditis elegans in soil and aquatic environment

Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants that have become a serious concern to human health and ecology. Due to strong C-F bonds and higher electronegativity, PFAS are highly stable and resistant to chemical, heat, and photo degradation. Thus, many PFAS have been produced over time for various consumer and industrial products across the world. Besides various applications, these properties also make PFAS highly bioaccumulative and persistent in nature. Numerous investigations and studies have identified various adverse effects of living organisms, including humans, linked with PFAS exposure. As a result, long-chained PFAS such as perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonate (PFHxS) were considered as the persistent organic pollutants (POPs) in Stockholm Convention in 2009. On the other hand, short-chain PFAS, such as perfluorobutane sulfonate (PFBS), are considered less bio-accumulative and non-hazardous to the ecology. After the phase-out of long-chain PFAS, short-chain analogs become more prevalent in the PFAS industry. As a result, the level of these short-chain analogs is drastically increasing in different environmental matrices day by day. Although many developed countries phased out long-chained PFAS, these are still detected in many parts of the world. Hence it has become necessary to evaluate the toxicity and safety level of both short and long-chained PFAS in the environment. In the present study, we examined the bioaccumulation pattern, acute behavioral toxicities, multi- and transgenerational toxicity, metabolic toxicity, oxidative stress, and genotoxicity of PFOS, PFHxS, and PFBS in Caenorhabditis elegans (C. elegans). Acute lethality and bioaccumulation rate were determined in both laboratory and environmentally relevant conditions. Our results demonstrated that the bioaccumulation rate and acute toxicities of PFAS depend on the length of the C-F chain. More number of C-F bonds makes PFAS chemicals more toxic to C. elegans. Besides, different behavioral endpoints such as locomotion, reproduction and lifespan of nematodes were found significantly affected by PFAS exposure. These behavioral toxicities were found to some extent to carry over to the progenies as well. Though all PFAS showed almost similar toxicity, short-chain analog required hundred times higher concentration to produce similar toxicity as long-chain PFAS precursors. Similarly, abnormal gene expression, DNA damage, oxidative stress, metabolic defects, and neurological toxicities were found more severe in nematodes exposed to long-chained PFAS in a concentration-dependent manner. Even in environmentally relevant conditions, toxicity and accumulation patterns are dominated mainly by the carbon chain length than soil/water properties. In few cases, short-chained PFAS showed some behavioral, oxidative, and metabolic toxicity, but at concentrations of hundreds fold higher than long-chained analogs. Therefore it can be recapitulated that short-chain PFAS are less bio-accumulative but could be hazardous similar to long-chain PFAS with higher exposure concentration.