A new study says chlorine doesn’t, in fact, kill the contents of our urine, but rather reacts with it to create potentially dangerous byproducts. The research, published in the journal Environmental Science & Technology, used a technique called membrane introduction mass spectrometry to measure the presence of dangerous byproducts in pools. Uric acid from human urine mixes with chlorine to create the cyanogen chloride (CNCI) and trichloramine (NCl3). CNCI is a toxic compound that can harm organs like the lungs, heart, and central nervous system. NCl3 has been linked with acute lung injury.