About two-thirds of benzene emissions can be attributed to mobile sources. In the metropolitan area, there has been a slight decrease in benzene concentrations since 1991, for which the reason is unclear. Given the magnitude of the measured concentrations, it would appear that benzene, a known human carcinogen, presents a potential health problem in both the Twin Cities metropolitan area and in smaller population centers. Minnesota's monitoring data do not show a decrease in concentrations since the ban. Carbon tetrachloride is very persistent in the atmosphere and can take decades to degrade.
Carbon tetrachloride is a probable human carcinogen and also causes damage to the liver and kidneys.
This location is in International Falls, adjacent to a U.S. paper mill and across the river from a Canadian paper mill, both of which are likely sources of the chloroform emissions. In addition to being classified as a probable carcinogen, chloroform may be involved in reproductive and developmental disorders. Target organs for chronic chloroform toxicity are the liver and the central nervous system. All rights reserved.