One recent review of the epidemiology of kidney cancer rated cigarette smoking and obesity as more important risk factors for kidney cancer than exposure to solvents such as trichloroethylene. In contrast, the most recent overall assessment of human health risks associated with trichloroethylene states, "here is concordance between animal and human studies, which supports the conclusion that trichloroethylene is a potential kidney carcinogen". The evidence appears to be less certain at this time regarding the relationship between humans and liver cancer observed in mice, with the US NAS suggesting that low-level exposure might not represent a significant liver cancer risk in the general population.