for the National Academy of Sciences reviews and addition of any new diseases to the presumptive list by the VA expired in 2015 under the sunset clause of the Agent Orange Act of 1991. Through this process, the list of 'presumptive' conditions has grown since 1991, and currently the U.S. Department of Veterans Affairs has listed prostate cancer, respiratory cancers, multiple myeloma, type II diabetes mellitus, Hodgkin's disease, non-Hodgkin's lymphoma, soft tissue sarcoma, chloracne, porphyria cutanea tarda, peripheral neuropathy, chronic lymphocytic leukemia, and spina bifida in children of veterans exposed to Agent Orange as conditions associated with exposure to the herbicide. This list now includes B cell leukemias, such as hairy cell leukemia, Parkinson's disease and ischemic heart disease, these last three having been added on August 31, 2010. Several highly placed individuals in government are voicing concerns about whether some of the diseases on the list should, in fact, actually have been included. In 2011, an appraisal of the 20-year long Air Force Health Study that began in 1982 indicates that the results of the AFHS as they pertain to Agent Orange, do not provide evidence of disease in the Operation Ranch Hand veterans caused by "their elevated levels of exposure to Agent Orange". The VA initially denied the applications of post-Vietnam C-123 aircrew veterans because as veterans without "boots on the ground" service in Vietnam, they were not covered under VA's interpretation of "exposed". In June 2015, the Secretary of Veterans Affairs issued an Interim final rule providing presumptive service connection for post-Vietnam C-123 aircrews, maintenance staff and aeromedical evacuation crews. The VA now provides medical care and disability compensation for the recognized list of Agent Orange illnesses. U.S.–Vietnamese government negotiations In 2002, Vietnam and the U.S. held a joint conference on Human Health and Environmental Impacts of Agent Orange. Following the conference, the U.S. National Institute of Environmental Health Sciences (NIEHS) began scientific exchanges between the U.S. and Vietnam, and began discussions for a joint research project on the human health impacts of Agent Orange. These negotiations broke down in 2005, when neither side could agree on the research protocol and the research project was canceled. More progress has been made on the environmental front. In 2005, the first U.S.-Vietnam workshop on remediation of dioxin was held. Starting in 2005, the EPA began to work with the Vietnamese government to measure the level of dioxin at the