Document mBwv8Kyd29ye71za7VEpw6Z6b

HONS 0 0 0 9 3 6 r\ ty kov$ D'"MTCH 0. Z5J71 AUG 17*377 Biphenyls harmful "hydrocarbons GttKtt Newt Service Special Polychlorinated biphenyls, first synthesized in.lttl, belong to a class of chemicals called chlorinated hythocaibons, which include most of the common pesticides and solvents. Many of the substances, such as DDT, Mirex, diekkin, aktrin and But scientists found that by substituting chlorine atoms for hydrogens in the biphenyl, they could create a substance that was flame* resistant Such molecules with more .than one chlorine atom are called polychlorinated biphenyls, or PCBs. tricMorethylene, have been banned About 1.4 billion poonds of after causing cancer in test animals. polychlorinated biphenyls have been Another sdstaoce, vinyl chloride, produced in this conntry in five has caused cancer in humans. decades. Pour per cent of the total The hydrocarbon part of the has been destroyed, 11 per cent is chemical is a molecule composed of free in the environment, and If per hjfrugcn and carbon, the buildhig cent is under varying drfrets of Mock of petroleum, gasoline and control in landfills. The rest is hi bil other fuels. Two attached "rings" of lions of items not yet (fiscarded. The hydrocarbons are extremely flam- EPA is stadyhig regulations to stop the discarding of more of the found. material but acknowledges that feat Hte chemicals are able to absorb will be difficult. and bold large amomts of beat, so In 1929, Monsanto Chemical Co. of they were used in beating coils to St. Louis began prodiicagTCBs com* heat products in factories, where an mercially, for use as a flame* open flame would have caused retardant and electrical insulator in ' transformers, capacitors and similar equipment It replaced mineral oils, which had resulted in many fires. So perfect were PCBs that witfahi a few years they became the fluid of PCBs extended the life of caulking compounds aromd the windows of skyscrapers. Since PCBs would not react with ink, they prevented choice in the electrical Industry. Id addition to preventing fires, flwyi were so stable as to be resistant to strong acids and bases and Mortgical degradation. . Soon, numerous other uses .verm smears on carbonless copy paper* They became a labriistMf sad rooting oil for industrial drills, la the Metric motors of refrigerators, air* oauditloncrs, typewriters, power mm, clothes washers and dryers, dishwashers and fernace blowers, PCBs became common. In capacitors, or "booalarV May / held an extra electric charge to help - start fluorescent lights. :