A ten-year-old mattress weighs double what it did when it was new due to debris that it absorbs over time. That debris includes dust mites (their droppings and decaying bodies), mold, millions of dead skin cells, dandruff, animal and human hair, secretions, excretions, lint, pollen, dust, soil, sand, and a lot of perspiration, which the average person loses at a rate of a quart a day.