N,N-diethyl-m-toluamide (DEET) is a key active ingredient in many insect repellents available commercially throughout the world. Owing to its popularity among consumers for nearly 30 years, considerable work conducted in the past has demonstrated-and continues to demonstrate-that human exposure to DEET poses no significant health risk to the general population. The results of several studies reported in this paper describe more recent work to understand the environmental fate of DEET, particularly in surface waters and soil, and the potential hazards to aquatic and terrestrial organisms. In summary, DEET enters the environment through several pathways: directly into air during spray application; to surface water from overspray and indirectly via wastewater treatment plant (WTTP) discharges (as a result of washing of skin and laundering of clothing); or to soil via overspray and application of treated sewage as an amendment. Multimedia environmental fate modeling predicts that DEET entering the environment is retained either in receiving waters (∼79%) or in soil (∼21%). Based on its physicochemical properties, DEET is expected to be moderately mobile in the soil column. In surface waters and soil, DEET degrades at a moderate to rapid rate (its half-life is measured in days to weeks). The small amounts of DEET retained in air are subject to rapid photo-oxidation via hydroxyl radical-mediated degradation or, if in droplet form, gravitational settling to soil or water. DEET does not interfere with ozone formation in the upper atmosphere. The bioaccumulation potential of DEET is low; it is neither a persistent, bioaccumulative toxicant nor a persistent organic pollutant. Among aquatic species, acute effect concentrations range between 4 and 388 mg/L. The chronic no-observed effect concentrations (NOEC) for daphnids and green algae range from approximately 0.5 to 24 mg/L. Measured concentrations of DEET in surface waters are several hundreds to thousands of times lower than the lowest NOEC measured, and thus the probability for adverse effects to environmental species is low. A separate paper by Aronson et al. (this issue) supports this conclusion by quantitatively exploring the risks to the aquatic environment using a combination of monitoring data and exposure modeling.

As a result of afforestation of the Crimean mountain plateaus in the middle of the last century, about 3 thousand hectares of forest plantations were created on their surface. Studies on the influence of these plantations on the properties of mountain-meadow soils (Phaeozems) have shown that under the forest vegetation there were an enlargement of structural aggregates, a decrease in humus content, and an increase in acidity compared to soils under meadow vegetation, which could also affect other soil properties, including the mobility of some metals. The purpose of this research is a comparative analysis of the content of mobile forms of Pb, Mn, Cu and Zn (1 M ammonium acetate) in the soils under mountain meadows, natural beech forest and artificial forest plantations. According to the results obtained, mobile Pb, Mn, and Cu were accumulated in forested mountainmeadow soils relative to adjacent areas of mountain meadows. So, in the soil layer of 0-10 cm under stands of pine (Pinus kochiana Klotzsch ex K. Koch), the average Pb content in comparison with soil under meadow vegetation was more than 1.6 times, Mn -1.2 times, Cu -in 1.2 times. Under the birch (Betula pendula Roth), Pb was 2.5 times more, Mn was 1.5 times more, and Cu was 1.2 times more. Under larch (Larix sibirica Ledeb), Pb was 2.2 times higher, Mn was 2.4 times higher, and Cu was 1.5 times higher. In comparison with the meadow, the soil under maple (Acer pseudoplatanus L.) contained 1.9 times more Pb, 1.1 -Mn, and 1.3 -Cu. Differences between forested and meadow soils in the content of these elements in most cases were reliable, except for the content of Zn, signs of accumulation of which under artificial plantings were not revealed. The content of Pb, Mn and Cu in the brown forest soil (Luvisols) under the beech (Fagus orientalis Lipsky) corresponded to their concentration under the larch, and Zn was significantly higher compared to the soil under all tree species. The main reason for increasing the mobility of a number of elements under tree stands is their transformation from low mobility forms under the influence of increased acidity of forested soils. Leaf litter due to the low content or complete absence of trace elements in its composition cannot be a source of their accumulation in the upper layer of the soil.