Dr. Fennell at the Chemical Industry Institute of Toxicology sought to develop new methods for improving the detection of formaldehyde-DNA adducts in exposed cells and tissues. The investigator treated formaldehyde-DNA adducts with sodium bisulfite, a compound that reacts with these adducts and traps them as stable compounds, and then tested different analytical techniques for separating and detecting the adducts. He exposed pure DNA, cell nuclei, and cells in culture to formaldehyde and treated them with sodium bisulfite under a variety of experimental conditions. When the use of radiolabeled formaldehyde proved to be unsuitable for experiments on cells or tissues, he evaluated several different modifications of 32P-postlabeling (a sensitive technique for detecting DNA adducts) to determine if he could isolate the adducts from formaldehyde-treated preparations. Finally, he explored alternative methods for modifying formaldehyde adducts to forms suitable for detection by either gas chromatography and mass spectrometry or immunoassays.