Confusion of identification of o,p′-Kelthane as heptachlor in orange rind extractives

Conclusions Both the glc and the tlc data prove that the unknown compound in the rind of Kelthane-treated oranges was not heptachlor. While the characterization is not absolutely conclusive, there can be no reasonable doubt that it iso,p′-Kelthane, known to be present in technical grade Kelthane. Other workers, using glc, reportedp,p′- ando,p′-Kelthane in the ratio of 100∶1 in 21 market fruit samples from different areas of Southern California. By analogy with DDT, if technical grade Kelthane is assumed to contain up to 20% of theo,p′-isomer this ratio found on fruits treated months previously means that on and in oranges theo,p′-isomer has much the longer half-life (RL₅₀) of the two isomers. On the other hand, approximately equal half-lives are indicated for the two isomers in soil. This brief study emphasizes the need for checking on gas chromatographic data by a more specific method and clearly demonstrates again that improper interpretation of data may be avoided by using at least two columns possessing different retention characteristics for the compounds of interest.     

Evaluation of a rubber-base impression material.

A laboratory experiment has been described that utilized materials found in most dental offices and that was designed to evaluate a distinctly different polysulfide impression material. In this experiment the largest duplicating errors were produced with use of the stock tray and single-mix technique recommended by the manufacturer. This study therefore supports the use of the custom tray and double-mix technique for dental duplication procedures utilizing Neo-Plex impression material. Further investigation is necessary before stock trays and single-mix techniques can be recommended for routine use in fixed prosthodontics.     

Worker environment research: Dioxathion (delnav®) residues on and in orange fruits and leaves,in dislodgable particulate matter,and in the soil beneath sprayed trees

Deposits and residues of dioxathion disappear at similar rates on and in the rind of oranges and the leaves of orange trees; dislodgable residues on the leaves dissipate at the same rate as the penetrated residues. This fact is important in evaluating the potential hazard to workers in treated groves because their exposure to pesticide residues is principally through the dislodgable residues. Samples of vapor and particulate matter taken during violent shaking of the trees show that the exposure of workers is almost entirely through contact with, and inhalation of, particulate matter, dermal contact probably being the more important. In one experiment, pickers were used in trees sprayed with dust containing no toxicant to determine the actual weights of dust that are inhaled (using Unico air samplers) and that accumulate on their bare arms (by washing at ten-minute intervals). The data show that several times as much dust is contacted dermally than is inhaled. Washing the entire trees with a dilute detergent solution removes a significant part of the dislodgable residue; as much as 30 percent is removed 46 days after spraying. The data presented in this paper provide a guide for toxicologists to permit the design of tests required to evaluate hazards workers encounter in pesticide-citrus groves.     

Use of laboratory toxicity tests with bivalve and echinoderm embryos to evaluate the bioavailability of copper in San Diego Bay, California, USA

Copper concentrations in parts of San Diego Bay (CA, USA) exceed ambient water quality criteria (WQC; currently 3.1 microg/L dissolved, U.S. Environmental Protection Agency [U.S. EPA]). In order to better understand the bioavailability of copper to water-column organisms in the bay, toxicity tests were performed with copper added to surface water collected from various sites in the estuary over a three-year period. The species and endpoints used, bivalve and echinoderm embryo-larval development, are among the most sensitive in the U.S. EPA's national toxicity dataset, which is used to derive WQC. No toxicity was observed in ambient bay water samples, as indicated by high proportions of normally developed larvae in control treatments, averaging 93+/-5% across all sites and all sampling events. Median effects concentrations (EC50), obtained by copper spiking of ambient water samples, ranged from 1.7 to 3.4 times lower at sites located near the mouth compared to sites near the back of the bay. These data indicate a gradient in complexation capacity increasing from the mouth to the back of the bay, which is consistent with similar trends in dissolved organic carbon and total suspended solids. For the bay as a whole, estimates for total recoverable and dissolved water-effect ratios (WER) ranged from 2.07 to 2.27 and 1.54 to 1.67, respectively. Water-effect ratios of this magnitude suggest that adoption of a somewhat higher site-specific WQC for San Diego Bay still would achieve the level of protection that is intended by the WQC guidelines.