The aquatic LD50 of PPD is 0.028 mg/L.[5] The U.S. Environmental Protection Agency reported that in rats and mice chronically exposed to PPD in their diet, it simply depressed body weights, and no other clinical signs of toxicity were observed in several studies.[9] One review of 31 English-language articles published between January 1992 and February 2005 that investigated the association between personal hair dye use and cancer as identified through the PubMed search engine found "at least one well-designed study with detailed exposure assessment" that observed associations between personal hair dye use and non-Hodgkin's lymphoma, multiple myeloma, acute leukemia, and bladder cancer,[10] but those associations were not consistently observed across studies. A formal meta-analysis was not possible due to the heterogeneity of the exposure assessment across the studies.