Pressed wood products like particle board and fiberboard are popular materials for big box furniture and home building because they offer a cheap alternative to solid wood. The problem is with how these products are made: manufacturers take bits and pieces of scrap wood and sawdust and press them together using chemical-laden glues and resins, including urea-formaldehyde. That formaldehyde then leaches into the air, leading to watery eyes, burning throat, and breathing difficulties. Worse, scientists warn that this dangerous chemical may be a carcinogen for humans, meaning it could cause certain types of cancer. The good news, if you already have particle board in your walls or furniture, is that pressed wood products emit less formaldehyde as they age. You can also minimize your risk of exposure to formaldehyde fumes by running a dehumidifier and air conditioner during the muggy summer months.