carcinogenesis is a class effect among the TZD's, just as water retention that causes CHF is a TZD class effect. However, compared to Avandia, Actos patients exhibit a cancer reporting rate in the AERS four times higher than Avandia patients. A possible explanation is that Actos is a salt-based chemical preparation with benzenesulfonate involved in the salt’s crystal formation, and its post-decomposition chemical particles are not totally biodegradable, resulting in excess benzene exposure, i.e. non-biodegraded toxic chemicals such as benzene remain in circulated blood and suppressed bone marrow and immune cells leading to cancer formations. On the other hand, Avandia is an ester-based chemical prepara- tion, with most of its chemical ingredients largely biodegraded and excreted during decompose- tion/metabolism, resulting in a lesser exposure to benzene. Since Avandia cancers/neoplasms appear to be reported at a lower rate than those reported for Actos, it is possible that carcino- genesis is one of the TZDs’ class effects depending on how the chemical compound was structured and formulated.