Woodsmoke looks cozy, but it's dangerous. Tiny particles called PM can get deep into your lungs, and even your bloodstream. PM10 is smaller than a red blood cell, and PM2.5 is even smaller. The World Health Organization calls it the most harmful pollutant, because it can reach every organ in your body. When inhaled, it can inflame your bloodstream and reach your heart and brain, increasing the risk of lung disease, strokes and even dementia. Children, older adults and anyone with health conditio