Video exposure assessments were conducted in a comparative anatomy laboratory using formaldehyde-preserved sharks and cats. Work in the facility using time-integrated samplers indicated personal and area concentrations generally below the current OSHA permissible exposure limit. However, complaints about room air quality were frequent and routine. Using a photoionization detector with an integral data logger, total ionizables present were sampled as a surrogate for formaldehyde. After synchronizing time tracks from the datalogger concentrations with simultaneously created videotapes of laboratory tasks, composite video exposure overlays were generated. Use of this video exposure method revealed very short-lived, excessively high peak exposure events, whereas conventional time-weighted averages indicated the majority (30/32) of personal exposures were below the OSHA limit of 0.75 ppm. These legally acceptable exposure levels were associated with self-reported symptoms of burning nose and eyes and eye irritation. Thus, transient peak formaldehyde concentrations not detected by longer term averaging studies could be responsible for the health effects reported. The video exposure monitoring method demonstrated that close dissection work, opening peritoneal cavities, and specimen selection activities were most likely the causes of elevated student exposures. Teaching assistants' exposures were the highest, exceeding OSHA limits on several occasions. The utility of the video monitoring method for conducting enhanced, critical task exposure assessments is discussed.

Understanding herbicide mobility in soils is necessary to prevent groundwater contamination. We studied the mass balance distribution of three 14C‐labeled herbicides (atrazine, metolachlor, and primisulfuron‐methyl) in four soils (Dothan, Portsmouth, Rion, and Wagram) 128 d after application to soil column field lysimeters. Analyses were made of surface soil, subsoil, and leachate samples, and metabolites were identified in surface soil and leachate. Our objectives were to examine, measure, and correlate the leaching patterns of the chemicals and correlate their leaching characteristics with the physicochemical properties of the soils. Metolachlor was the most mobile herbicide as indicated by the retardation factor (Rf) (Rf = 0.35 in 1992 and 0.17 in 1993), followed by atrazine (Rf = 0.19 in 1992 and 0.09 in 1993) and primisulfuron‐methyl (Rf = 0.15 in 1992 and 0.12 in 1993). Herbicide mobility (Rf) was related to leachate volume collected from the four soils, herbicide aqueous solubility, and longevity of the chemicals. The herbicides were of greatest mobility in Rion and Wagram soils and of lowest mobility in Portsmouth and Dothan soils. Soil factors affected the weakly basic atrazine differently than the nonionizable metolachlor or the weakly acidic primisulfuron‐methyl. Volatility losses of the herbicides were inversely related to longevity (disappearance time in the field (DT50) of the compounds and to humic matter contents of the soils. Carbon‐14 herbicide in the subsoil and in the leachate was correlated with herbicide mobility (Rf), total leachate volume, and 50% disappearance time values. Herbicide mobility was in agreement with predictability using a simple decision‐aid model.

Leaching studies using soil column field lysimeters were conducted in 1991 and 1992 to determine the influence of tillage [conventional (CT) and reduced (RT)], soil cover (fallow, soybean, and bermudagrass sod), and water input level on 14C metolachlor mobility. Runoff and leachate collectors were installed. Leachate was collected weekly and analyzed for herbicide content. At 128 d after treatment (DAT), the lysimeters were removed, and the soil was analyzed for herbicide concentration as a function of depth. In 1991, 10% greater amounts of 14C metolachlor volatilized from CT than from RT (32 vs. 22%). Amounts of metolachlor recovered in surface cover were 2.3% less (2.1 vs. 4.4%), amounts in subsoil were 8% less (47 vs. 55%), and amounts recovered in leachate were 0.7% less (0.7 vs. 1.4%) under CT than RT. In 1992, measured parameters of 14C distribution in soil for tillage treatments were similar, except 14C recovered in leachate was 3% greater under RT (7 vs. 4%). Amounts of 14C metolachlor retained by soil cover were greatest in bermudagrass sod (16%), less in soybean (4%), and least in fallow (1%) and were similar for each treatment both years. Carbon‐14 metolachlor recovered in leachate of all treatments was approximately five times greater in 1992 (5%) than in 1991 (1%) due to the 7% greater water input in 1992, much of which occurred shortly after Day 0. Leachate volume collected in 1992 (8 L) was also twice that of 1991 (4 L). Tillage and soil cover interaction effects occurred both years.