Zoos across the country have banned the use of wood treated with arsenic, saying it is unsafe for animals. But much of the "pressure treated" wood sold in hardware stores and lumber yards today for things like decks, picnic tables and playground equipment is soaked in a chemical called chromated copper arsenate, which contains arsenic.

Studies have shown that children can ingest this chemical when it rubs off the wood and gets on their hands. Ingestion of arsenic can lead to high blood pressure, reproductive problems and even cancer.

Luckily, retail chains like Home Depot and Lowes have responded to pressure from environmental groups and voluntarily agreed to phase out the sale of arsenic-treated wood over the next couple of years. Nonetheless, many stores still have arsenic-treated wood in their current inventory until it gets sold off.

When shopping for lumber for home improvement projects, you should ask which types of wood were treated with arsenic and avoid purchasing them. If you find arsenic-treated wood already in use in your home or community, it is of course safest to replace it. But sealants are also available that can reduce the amount of arsenic that rubs off the wood by up to 95% if applied every couple years.