As requested in Mr. F. D. Kovar's letter of September 23, 1981, we are enclosing information on trimethyl phosphite hydrolysis and on levels of trimethyl phosphate measured at our production site. Attachment No. 1 summarizes the hydrolysis studies. The data indicate that hydrolysis occurs rapidly at ordinary temperatures only under acid catalyzed conditions. Attachment No. 2 provides exposure data collected over the past three years on trimethyl phosphite using 165 employee exposure samples. The table lists the time weighted averages (TWA) in ppms measured on various days and identifies the unusual conditions giving rise to the elevated values. As footnoted, the asterisks values denote periods when protective equipment was used to guard the employees from trimethyl phosphite exposure. Aside from those data points, the highest TWA was 2.17 ppm, with the majority of the measurements well below 1 ppm.