It has been great to see, over the years, the number of comprehensive recycling programs that have sprung up in municipalities around the world. The number of common household items that we are now able to recycle and eliminate from landfills has been steadily growing, but there are still a number of items that people think are recyclable, when they actually are not. Below are 5 things you thought you could put in the recycling bin but can’t.

Pizza boxes. Pizza boxes are made of cardboard, and cardboard, in most other forms, is certainly recyclable. However, pizza boxes contain oil from the pizza, which soaks into the cardboard, and, when included with other cardboard in the recycling process, can contaminate the entire batch of recycling.

Plastic bottle caps. You can certainly recycle your plastic water bottle, but the cap is unrecyclable. The caps on most plastic bottles are made from plastic #5, which many household pickup recycling programs will not take. This also includes plastic tops on things like detergent bottles and tubs of peanut butter.

Styrofoam. Styrofoam is everywhere and it’s an environmental disaster. Styrofoam is made from petroleum and it is highly flammable and most, if not all, municipal pick-up recycling programs will refuse to take it. Check around your community to see if there is a Styrofoam recycling location near you so that you can safely dispose of it.

Aerosol cans. Even those these cans are made out of recyclable metal, they contain harmful chemicals and therefore cannot be taken to the curb with the rest of your recycled metal, which probably takes the form of aluminum and tin cans.

Wet paper. If the paper you are planning on recycling has ever been wet at any point, it can’t be. The fibres become damaged once the paper is wet and it can, like the oil in the pizza boxes, contaminate the rest of the recycling.

We should all try and recycle as much as we can, whenever we can. It’s always a good idea to try and improve your recycling knowledge and keep adding to the list of common household items that are recyclable. However, there are some items that simply cannot be recycled, even though they may contain recyclable parts, or seem identical to other recyclable materials. Keep the above five items in mind when recycling things around your home and do your part for the environment.