Presence Of Transformation Products Research Articles

Effect of chlorination on anti-acetylcholinesterase activity of organophosphorus insecticide solutions and contributions of the parent insecticides and their oxons to the activity

Organophosphorus insecticides are known to be partly transformed to their respective oxons during the chlorination step of drinking water treatment. For most organophosphorus insecticides, the toxicological endpoint for determining acceptable daily intake levels is inhibition of acetylcholinesterase (AChE). Like the parent insecticides, oxons also inhibit AChE, so the presence of oxons in drinking water is also evaluated. However, no attention is paid to the possible presence of transformation products (TPs) other than oxons. In the present study, we determined whether the anti-AChE activity observed for chlorinated solutions of the organophosphorus insecticides malathion and methidathion could be solely attributed to the parent compounds and their oxons. Upon chlorination, both malathion and methidathion were immediately transformed to their oxons; the maximum transformation ratios were 60% and 30%, respectively, indicating that at least 40% and 70% of these compounds were transformed into other TPs. Before chlorination, malathion- and methidathion-containing solutions exhibited little to no anti-AChE activity, but the solutions showed strong activity after chlorination. The contributions of the parent insecticides and their oxons to the activities of the chlorinated samples were calculated from the concentrations of the compounds in the samples and dose–response curves for chemical standards of the compounds. For both the malathion-containing solution and the methidathion-containing solution, the calculated anti-AChE activities were almost the same as the observed activities at every chlorination time. This suggests that the observed activities could be attributed solely to the parent insecticides and their oxons, indicating that other TPs need not be considered.

Screening and human health risk assessment of pharmaceuticals and their transformation products in Dutch surface waters and drinking water

Numerous studies describe the presence of pharmaceuticals in the water cycle, while their transformation products are usually not included. In the current study 17 common pharmaceuticals and 9 transformation products were monitored in the Dutch waters, including surface waters, pre-treated surface waters, river bank filtrates, two groundwater samples affected by surface water and drinking waters. In these samples, 12 pharmaceuticals and 7 transformation products were present. Concentrations were generally highest in surface waters, intermediate in treated surface waters and river bank filtrates and lowest or not detected in produced drinking water. However, the concentrations of phenazone and its environmental transformation product AMPH were significantly higher in river bank filtrates, which is likely due to historical contamination. Fairly constant ratios were observed between concentrations of transformation products and parent pharmaceuticals. This might enable prediction of concentrations of transformation products from concentrations of parent pharmaceuticals.The toxicological relevance of the observed pharmaceuticals and transformation products was assessed by deriving (i) a substance specific provisional guideline value (pGLV) and (ii) a group pGLV for groups of related compounds were under the assumption of additivity of effects within each group. A substantial margin exists between the maximum summed concentrations of these compounds present in different water types and the derived (group) pGLVs. Based on the results of this limited screening campaign no adverse health effects of the studied compounds are expected in (sources of) drinking water in the Netherlands. The presence of transformation products with similar pharmacological activities and concentration levels as their parents illustrates the relevance of monitoring transformation products, and including these in risk assessment. More thorough monitoring yielding information on statistical uncertainty and variability in time and space, and research on possible synergistic effects of low concentration mixtures of compounds belonging to similar pharmacological classes require attention.

Identification of several Tonalide® transformation products in the environment

Organic synthesis has been applied to detect potential Tonalide (AHTN) transformation products in a semi-quantitative way in environmental samples by using a well-established trace-analytical method, developed for the quantification of the parent compound AHTN. For the first time, indications for the presence of transformation products of the synthetic musk compound 1-(5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphthalenyl)ethanone (1) (Tonalide®, AHTN) have been found in the environment. Pure standards of the detected products were obtained by multistep syntheses from Tonalide®. Two main derivatives, 3-acetyl-5,6,7,8-tetrahydro-5,5,7,8,8-pentamethyl-2-naphthalenecarbaldehyde (2) and (3-ethyl-5,6,7,8-tetrahydro-5,5,7,8,8-pentamethyl-2-naphthalenyl)methanol (4), and three minor products, (5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphtalenyl)methanol (6), 5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphtalenecarbaldehyde (7), and methyl 5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphthalenecarboxylate (8), were identified in three human breast-milk samples and three fish samples. All samples contained one or several of these transformation products at a concentration range of around 10 pg g−1 wet weight. Email:leiv.sydnes@kj.uib.no

Persistence of Parent Compounds and Transformation Products in a Level IV Multimedia Model

An approach to extend the concept of persistence to transformation products of environmental chemicals is presented. First, the residence time in a steady-state scenario and the lifetime in a pulse scenario as two commonly used persistence measures are compared with respect to their mathematical formulation, and concentration functions as time-dependent solutions of a dynamic multimedia model are calculated. Second, it is shown how the model system needs to be modified in order to calculate concentration functions for any number of transformation products. On the basis of these concentration functions, two new persistence measures describing the additional exposure of the environment that is caused by the presence of transformation products are introduced. These two measures, called Joint Persistence and Secondary Persistence, are explicitly calculated for two pairs of parent compounds and transformation products, namely, methyl tert-butyl ether (MTBE) and atrazine and their transformation products tert-b...

Atmospheric Dispersion of Current-Use Pesticides: A Review of the Evidence from Monitoring Studies

Recently, evidence has accumulated that the extensive use of modern pesticides results in their presence in the atmosphere at many places throughout the world. In Europe over 80 current-use pesticides have been detected in rain and 30 in air. Similar observations have been made in North America. The compounds most often looked for and detected are the organochlorine insecticide lindane and triazine herbicides, especially atrazine. However, acetanilide and phenoxyacid herbicides, as well as organophosphorus insecticides have also frequently been found in rain and air. Concentrations in air normally range from a few pg/m3 to many ng/m3. Concentrations in rain generally range from a few ng/L to several μg/L. In fog even higher concentrations are observed. Deposition varies between a few mg/ha/y and more than 1 g/ha/y per compound. However, these estimates are usually based on the collection and analysis of (bulk) precipitation and do not include dry particle deposition and gas exchange. Nevertheless, model calculations, analysis of plant tissue, and first attempts to measure dry deposition in a more representative way, all indicate that total atmospheric deposition probably does not normally exceed a few g/ha/y. So far, little attention has been paid to the presence of transformation products of modern pesticides in the atmosphere, with the exception of those of triazine herbicides, which have been looked for and found frequently.