intervening years, including among the US Air Force crews that handled them. Scientific reports have concluded that refugees exposed to chemical sprays while in South Vietnam continued to experience pain in the eyes and skin as well as gastrointestinal upsets. In one study, ninety-two percent of participants suffered incessant fatigue; others reported monstrous births. Meta-analyses of the most current studies on the association between Agent Orange and birth defects have found a statistically significant correlation such that having a parent who was exposed to Agent Orange at any point in their life will increase one's likelihood of either possessing or acting as a genetic carrier of birth defects. Although a variety of birth defects have been observed, the most common deformity appears to be spina bifida. Chloro-dioxins, which are inevitably formed as a byproduct of Agent Orange synthesis, are highly teratogenic, and there is substantial evidence that the birth defects carry on for three generations or more. In 2012, the United States and Vietnam began a cooperative cleaning up of the toxic chemical on part of Danang International Airport, marking the first time Washington has been involved in cleaning up Agent Orange in Vietnam. Vietnamese victims affected by Agent Orange attempted a class action lawsuit against Dow Chemical and other U.S. chemical manufacturers, but the District Court dismissed their case. They appealed, but the dismissal was cemented in February 2008 by the Court of Appeals for the Second Circuit. , the Vietnamese government estimates that there are over 4,000,000 victims of dioxin poisoning in Vietnam, although the United States government denies any conclusive scientific links between Agent Orange and the Vietnamese victims of dioxin poisoning. In some areas of southern Vietnam, dioxin levels remain at over 100 times the accepted international standard. The U.S. Veterans Administration has listed prostate cancer, respiratory cancers, multiple myeloma, Diabetes mellitus type 2, B-cell lymphomas, soft-tissue sarcoma, chloracne, porphyria cutanea tarda, peripheral neuropathy and spina bifida in children of veterans exposed to Agent Orange. Casualties Estimates of the number of casualties vary, with one source suggesting up to 3.8 million violent war deaths in Vietnam for the period 1955 to 2002. A detailed demographic study calculated 791,000–1,141,000 war-related deaths during the war for all of Vietnam, for both military and civilians. Between 195,000 and 430,000 South Vietnamese civilians died in the war. Extrapolating from a 1969 US intelligence report, Guenter Lewy estimated 65,000 North Vietnamese