Creates, for veterans who were subjected to certain chemical or biological warfare testing involving Project 112 conducted through Deseret Test Center (including the Shipboard Hazard and Defense Project, also known as Project SHAD), a presumption that a disease was incurred in or aggravated by service, notwithstanding that there is no record of evidence of the disease during the period of service, if the disease warrants presumtion of service connection by reason of increased exposure to a biological, chemical, or other toxic agent.