BOSTON - The claims of a former refrigeration technician that benzene exposure caused acute promyelocytic leukemia (APL) have been dismissed by a Massachusetts federal judge, who said in a Sept. 6 opinion that use of differential diagnosis by the plaintiffs' expert to rule out other causes was unreliable because most cases of APL have no known origin (Brian K. Milward, et al. v. Acuity Specialty Products, et al., No. 07-cv-11944, D. Mass.; 2013 U.S. Dist. LEXIS 127473).