Effects of Short Chain Chlorinated Paraffins (SCCPs) on developing birds

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The Challenge: Short-Chain Chlorinated Paraffins (SCCPs) are complex technical mixtures of polychlorinated n-alkanes used in lubricants and coolants in metalworking, as flame retardants, and in paints, adhesives, sealants, textiles and polymeric materials, plastics and rubber. SCCPs are of concern because they are globally transported, bioaccumulate in wildlife and humans, and are environmentally persistent. Their toxicity has been demonstrated in multiple species and their presence has been detected in wild birds and their eggs far from primary manufacturing centers. However, few controlled studies have been conducted to determine the potential hazard and risk that SCCPs pose to free-ranging birds.

The Science: USGS biologists from Patuxent Wildlife Research Center collaborated with scientists from Environment and Climate Change Canada to investigate the effects of embryonic exposure to SCCPs in birds. Eggs collected from American kestrel (Falco sparverius) were injected with SCCPs at environmentally realistic concentrations and artificially incubated until hatching. Egg injections provide an approximation of the effects resulting from maternal deposition of a chemical in nature. Hatchling survival, growth, somatic indices and deformities were assessed. Molecular and biochemical indicators including changes in gene expression (RNAseq), oxidative stress levels, and thyroid hormone-related biomarkers were analyzed.

The Future: We found that exposure of developing American kestrels to SCCP concentrations found in wild bird eggs, affected their thyroid function at hatch. This has also been reported previously in mammals and suggests conservation of toxic modes of action across species. The thyroid system is important for thermoregulation, growth and survival of birds and the occurrence of these effects in captive kestrels suggests the possibility of similar effects in wild birds.

The U.S. EPA has issued a Significant New Use Rule governing SCCPs under the Toxic Substances Control Act (TSCA). The Persistent Organic Pollutant Review Committee (POPRC) of the UN Stockholm Convention added SCCPs to its list of Persistent Organic Pollutants (POPs), calling for a global ban on manufacture and use. Results from our study provide important information to risk assessors on potential pathways that are adversely affected by SCCPs in wildlife.