HAPAB The results of a pilot study on pesticide pollution of the air conducted for the Public Health Service by Midwest Research Institute ( MRI) are reported. MRI established sampling stations in four urban and five rural locations. The urban locations included Baltimore, Md., Fresno, Calif., Riverside, Calif., and Salt Lake City, Utah. The rural stations were situated near Buffalo, N. U., Dothan, Ala., Iowa City, Iowa, Orlando, Fla., and Stoneville, Miss. MRI was monitoring for DDT, DDE, DDD (TDE), benzene hexachloride isomers, dieldrin, endrin, heptachlor, aldrin, heptachlor epoxide, chlordane, 2,4-D esters and salts, parathion, methyl parathion and malathion. Toxaphene and DEF were also detected. Four sampling sites were selected at each location and air sampling units of MRI's own design were then installed in a suitable location at each site. The sampling schedule was set up so that samples were obtained during the growing season. Collections were made during two 1-week intervals of each consecutive 4-week period for 24 weeks. The sampling stations used in the 1-week intervals were randomized and not all samples were collected during a consecutive 24- week period. Samples collected weekly were analyzed for pesticide content by gas chromatography. Results showed that DDT was the only pesticide found at all localities. Heptachlor epoxide, chlordane, DDD and 2,4-D esters were not detected. Aldrin and 2,4-D were found in only one sample. Methyl parathion was found only in samples from Dothan, Orlando and Stoneville, while parathion and malathion were found only at Orlando and DEF, a cotton defoliant, only at Stoneville. Levels were generally lower in urban than in rural areas. Except for Orlando, levels were higher during the summer and the highest levels were found in the agricultural areas of the South, while relatively low levels were found in other agricultural areas. Levels were higher while pesticide spraying was in progress and there was no apparent correlation of level with rainfall. To determine diurnal variation of pesticide concentrations, samples were collected in Baltimore and Fresno for 4-hr periods each day. However, pesticide levels were so low that a composite sample from two sampling locations for 3 days had to be made. The conversion of the three title compounds, the first two of which are widely used as nematocidal soil fumigants, to ethylene, n-propanol and butenes, respectively, in soil was investigated. The preparation of the soil screen, the C-14 labeled compounds and the analytical procedures for determining bromide ion and the three conversion products are described in detail. Using 1,2- dibromo-3-chloropropane ( DBCP ) as the scanning substrate, some 100 soils were tested for their ability to reductively dehalogenate the compound. The most effective soil ( from an old lemon grove ) was used in all subsequent work. At pH above 7.0, soil organisms converted ethylene dibromide to ethylene quantitatively in a period of about 2 months. The most rapid dehalogenation of DBCP, 20% in one week, occurred in soil at pH 8, but DBCP's maximum conversion was only 63% in 4 weeks. The conversion of 2,3-dibromobutane was not studied quantitatively because over an 8-week period significant hydrolysis occurred in the blands. However, it was established that inoculated soil-water suspension containing dibromobutanes resulted in butene production. The biological nature of the conversion, which was deduced from a series of experiments, indicated that halide release occurs only under conditions that will support growth and only when the substrate is present during the growth phase. It is inhibited by sterilization of the soil with ethylene oxide or by autoclaving, by omission of a carbon source ( glycerine ) or by treatment of active cultures with sodium azide or heat. It was concluded that the transformation may be a detoxification process or the result of a secondary interaction of biologically engendered substances with the substrate. MONITORING AND RESIDUES MONITORING AND RESIDUES 69/03/00, 71 69/03/00, 71 1968
