The reaction of chloroacetaldehyde (CAA) with DNA results in the formation of ethenoadenosine also known as 1,N6-ethenodeoxy-adenosine or etheno-A. CAA is formed through metabolization of for example vinyl chloride, a well established carcinogen. In RNA, after in vitro activation, etheno-A and etheno-C are the principle products of RNA damage. Etheno derivate formation may be highest in single-stranded DNA-regions.The monoclonal antibody 1G4 reacts with both the ribose and deoxyribose form of the adduct. The antibody is not cross reactive with non-modified DNA or the normal nucleotides.