A few carcinogens commonly found in tar include benzene, acrylamide and acrylonitrile. Hydration of acrylonitrile results in formation of acrylamide molecules () by nitrile hydratase. Acrylonitrile is also a precursor in the industrial manufacture of acrylamide and acrylic acid. Increased concentrations of acrylamide result in decreased pore size after polymerization. Molecular oxygen, iodide ions and acrylamide are common chemical quenchers. The gels are slightly more opaque than acrylamide or agarose. At high temperatures, a probable carcinogen called acrylamide can form. Concern was raised mainly because of the probable carcinogenic effects of acrylamide. The majority of acrylamide is used to manufacture various polymers. This allows for low molecular weight proteins to be separated in lower percent acrylamide gels. Similarly, phosphinic acid adds to Michael acceptors, for example with acrylamide it gives H(HO)P(O)CHCHC(O)NH. These enzymes are used commercially to produce acrylamide. Symptoms of acrylamide exposure include dermatitis in the exposed area, and peripheral neuropathy. This reaction is employed in the production of acrylamide. These microfibrils are embedded into a soft acrylamide matrix for structure.