what is dangerous pfas - perfluoroalkyl and polyfluoroalkyl substances

pfas pfass concept concepts pollutants pollution polyfluoroalkyl pfoa pfos contamination organofluorine chemicals attention environmental damage issues illness carcinogen water repellent chemical danger warning synthetic cancer toxic waterproof impermeable waterresistant rainproof compounds fluorinated substances fluorine organic environment health exposure risk dangerous products fluorochemicals carcinogenic biochemistry pollutant microbiology chemistry hazard perfluoroalkyl where found found? pfas are