If holidays had elements, Halloween would have to claim Selenium (Se).

Se’s biochemistry shows some of the creepiest moves on the periodic table.

The first thing to know is that Se is an essential micronutrient for animals. That means all animals need it for normal functioning, but cannot produce it, so they must consume it in their diet.

Once those dietary needs are met, however, Se becomes toxic at the drop of a hat.

Here’s how: Once consumed, Se sneaks into spots normally held by sulfur, which build the shape of proteins (typically through incorporation into the amino acid selenocysteine) – and this leads to some frightening outcomes as you see above. Se is just similar enough to sulfur to fit into protein folds, but different enough to cause major damage.

Selenium toxicity hits the earliest life stages hardest, doing its worst to wildlife when passed down by mothers to their eggs, larvae, and juveniles. This is because Se is gathered up from the mother’s body and sent into her offspring through vitellogenesis – the process of yolk development in eggs.

Se toxicity in fish and wildlife is downright scary. Se-contaminated fish often show misshapen backbones and jaws, or more severe malformities. Waterfowl can also suffer embryonic deformities and organ damage that reduce their survival. That’s because waterfowl often rely on wetland habitats that are connected to streams where Se loads can be highest. When it comes to mutated fish and wildlife, Se is all trick and no treat.

So how did it get into streams and wetlands in the first place? That may be the scariest part. Se naturally occurs in some rock formations across Appalachia – particularly in coal deposits of the Allegheny and upper Kanawha formations. And when the coal is mined, rain dissolves Se from the rocks and flushes it into streams and rivers, where it becomes incorporated into foodwebs, impacting fish and wildlife.

And it gets even worse. DEP is poised to weaken the water quality standard for Se during the upcoming legislative session – they aim to allow for more Se in fish, and this is important because this is how compliance with the water quality standard is measured. This all stems from a request by the WV Coal Association to weaken water quality standards in certain mining areas, and DEP apparently will propose extending those weakened standards across the state.

But here’s the good part: WV Rivers will be watching this closely, and we will need your help to push back against this scary proposal to allow more Se toxicity in the 2026 legislative session.