Appendix 2 Open Literature Review Summaries for Malathion
Description of Use in Document
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| Description of Use in Document: Valid for arrays (qualitative)
Rationale for Use: Given that the units, exposure route, were in ppm, the units could not be converted to environmentally-relevant units of lb a.i./A. Additionally, the seed coats were removed prior to exposure, and there is uncertainty in the environmental relevance of this exposure. Limitations of Study: The malathion product used in the study was poorly described, listed only as “Malathion, obtained from Cyanamid India Ltd, Bombay”. The percent active ingredient of the formulation (or if it is representative of a U.S. formulation) was not provided; neither was a registration number provided that could be used to definitively identify the test substance. Also note that the study authors used “ppm” as the units to describe the concentration of malathion in the different treatments. It appears that the different treatments were not replicated; instead, the experiment was repeated six times and the reported data are means ± SD of the different trials. Growth and respiration data were not reported, although percent reductions (compared to the control) were plotted. Only a summary table of treatment level results was included and the statistical analyses employed by the study authors were not described (e.g., t-test, ANOVA, chi square). Analytical confirmation of the concentration of malathion in the treatments was not described. Primary Reviewer: Nathan Miller, ERB6 Secondary Reviewer: Elizabeth Donovan, ERB6 Open Literature Review Summary Chemical Name: Malathion 5% dust CAS No: Not reported PC Code: 057701 ECOTOX Record Number and Citation: 089329. Ramzan, M., and B.S. Chahal. 1989. Effect of Grain Protectants on Viability of Wheat Seeds. Seed Research. 17 (1): p 47-54. Purpose of Review (DP Barcode required for Quantitative studies): Malathion ESA pilot (Registration Review) Date of Review: February 5, 2015 Summary of Study Findings: The effect of applications of malathion to wheat seed subjected to storage at 10 and 15% moisture content for one year under air-tight and non air-tight conditions was evaluated. Malathion (5% dust) treatment was applied after spraying water over the wheat seeds to obtain the desired moisture content (10% or 15%). Malathion dust was applied at three different concentrations: 50, 125, and 250 ppm. After a week of moisture stabilization, the wheat seeds were transferred to 48 (20 cm X 15 cm) polythene bags of 400 gauge thickness, filled to 500g each. The study report states: “There were 4 replication.” It is unclear whether this means that each malathion treatment was replicated four times. 24 bags were sealed by machine to be airtight and 24 bags were loosely tied with rubber bands to provide non airtight conditions. Seeds of an untreated control were stored under both conditions. During the 1979-80 experiment, the germination of seeds treated with malathion at all concentrations except 50 ppm was significantly lower than the control. During the 1980-81 experiment, the germination of seeds treated with malathion at all concentrations except 50 ppm was significantly lower than the control. Based on the statistical significance reported by the study authors, the LOAEC for malathion effects to wheat seed germination is 125 ppm. Statistical methods were not described beyond a footnote to the results table which states: “The data were analyzed after angular transformation of percentage values; the back transformation values of transformed data are given.” Table 1. Effect of malathion used as a grain protectant on the viability of wheat seed
*The data were analyzed after angular transformation of percentage values; the back transformation values of transformed data are given MC- Moisture content Description of Use in Document: Valid for arrays (qualitative) Rationale for Use: Based on limitations below Limitations of Study: As described in the 2007 California Red Legged Frog assessment, malathion terrestrial plant toxicity studies in the open literature are of limited utility because the selected exposure route(s) are of questionable environmental relevance. This study is no exception; the dusting of seeds followed by storage under discreet moisture conditions for six to twelve months prior to germination is not environmentally relevant. The malathion product used in the study was poorly described, listed only as “Malathion 5% dust”. It is unclear whether the percent active ingredient of the formulation was in fact 5%, or some other value. Also note that the study authors used “ppm” as the units to describe the concentration of malathion in the different treatments. According to the OPP open literature review guidance3, the report should state which methods of statistical comparison (e.g., t-test, ANOVA, chi square) were used and the presumed nature of the data (parametric versus nonparametric); however, only a summary table of treatment level results was included and the statistical analyses employed by the study authors were not described. Primary Reviewer: Nathan Miller Secondary Reviewer (required if study results are used quantitatively): Elizabeth Donovan, ERB6 Open Literature Review Summary Chemical Name: Malathion CAS No: Not reported PC Code: 057701 ECOTOX Record Number and Citation: 090706. Lloyd, R.W., and D.R. Krieg. 1987. Cotton Development and Yield as Affected by Insecticides. Journal of Economic Entomology. 80: p 854-858. Purpose of Review (DP Barcode required for Quantitative studies): Malathion ESA pilot (Registration Review) Date of Review: February 6, 2015 Summary of Study Findings: The effect of malathion applied to cotton plants (cultivar TAMCOT SP37) at a rate of 0.65 kg ai/ha (0.58 lb ai/A) in greenhouse plots (four applications, reapplication interval of 10 days) and field plots (five applications, reapplication interval of 10 days) was evaluated. Treatment was initiated when the first floral bud was observed. Physiological responses (e.g. gas exchange rates) of the cotton plants were measured 24 and 48 hours after application. Complete growth analyses were conducted 30 and 60 days after the initial application (DAIA). Growth measurements included height, number of nodes per plant, total number of leaves, leaf area, and floral bud and fruit numbers from all plants per square meter of ground area per plot. Yield was evaluated as a function of the number of bolls per 10 square meters ground area and boll weights (grams per 100 bolls). All data were subjected to analysis of variance with Duncan’s multiple range test and least significant difference used to separate means at the P = 0.05 level. Malathion treatment resulted in no significant effect on carbon assimilation rate, stomatal conductance, or the efficiency of the gas exchange process as indicated by intercellular CO2 concentration. Malathion treatment was associated with a greater number of floral buds at 60 DAIA compared to the control. Malathion also increased fruit numbers per plant at 30 DAIA; by 60 DAIA, this increase was significant compared to the control. No significant interactions were observed for any of the yield components. Based on the significant increase in the number of bolls per cotton plant observed in the malathion treated plots at 60 DAIA in comparison to the control, the lowest observed effect level (LOEL )is associated with five applications of 0.58 lb ai/A and a 10-day retreatment interval. Description of Use in Document: Valid for arrays (qualitative) Rationale for Use: The effects described in this paper are increases in number of bolls/fruit and would not be characterized as adverse as it pertains to the risk assessment. Limitations of Study: The malathion test substance used in the study was poorly described, listed only as “malathion.” No EPA registration number was provided to facilitate identification of the tested product. The percent active ingredient of the malathion test substance used was not provided. Primary Reviewer: Nathan Miller, ERB6 Secondary Reviewer: Elizabeth Donovan, ERB6 Open Literature Review Summary Chemical Name: Malathion (Commercial formulation (Spectracide ®); Technical grade (purity >98%, Chemservice, PA) ) CAS No: Not reported PC Code: 057701 ECOTOX Record Number and Citation: 162475. Jennings, D.E., A.M. Congelosi and J.R. Rohr. 2012. Insecticides reduce survival and the expression of traits associated with carnivory of carnivorous plants. Ecotoxicology. 21: 569-575. Purpose of Review (DP Barcode required for Quantitative studies): Malathion ESA pilot (Registration Review) Date of Review: November 17, 2015 Summary of Study Findings: This study, using a combination of lab- and field-based experiments, tested the effects of technical grade (>98%) and formulated malathion (Spectracide, 50% a.i.) on the survival of pink sundews (Drosera capillaris) and Venus flytraps (Dionaea muscipula). It also evaluated the effects of technical grade and formulated malathion on the expression of carnivorous traits (e.g., the number of mucilage-producing leaves in pink sundews or the number of traps in Venus flytraps). Only results on survival are discussed in this review. Studies were conducted for 4 weeks and plants were considered dead when all structures turned black. Pink sundews were collected from the University of South Florida Ecological Research Area (ERA) and Venus flytraps were ordered from www.bugbitingplants.com. All lab experiments were maintained at 23°C under full spectrum lighting (14L/10D) and covered in Plexiglas to maintain humidity. Experiment I (lab): Seventy-two pink sundews (mean diameter 2.28 ± 0.59 cm) were planted in individual 9 cm diameter plastic cups filled to 5 cm with sand, as often they are locally found in extremely sandy soils. Treatments consisted of a de-ionized (DI) water control and a commercial grade of malathion with 18 replicates. At the start of the experiment, 5 ml of the insecticide was applied directly to the sundews using a spray bottle and following the recommended application instructions on each product. This resulted in a nominal application rate of 5.19 kg/ha (4.63 lb a.i./A) for malathion. According to the study authors, the rates of insecticide application used for this experiment represented an overspray scenario for mosquito control, but were comparable to the rates used for control of agricultural pests. Experiment II (lab): Technical malathion was applied to five randomly chosen sundews at concentrations of 51.9 (0.03%), 5.19 (0.003%), 0.519 (0.0003%), 0.0519 (0.00003%) kg of a.i./ha (based on serial dilutions of the highest concentration). The rates of insecticide application used in this experiment represented a range of scenarios. Additionally, there were five replicates of both DI water and acetone (10%, solvent used to get chemicals in solution) controls. Sundews (mean diameter 2.13 ±0.39 cm) were planted in individual 9 cm diameter plastic cups filled to 5 cm with sand, and at the start of the experiment, 5 ml of the appropriate insecticide was applied directly to the sundews using pipettes. Pipettes were used in this experiment for logistical purposes, and the study authors stated theywere confident that similar amounts of insecticides reached both the plants and the substrate compared to the spray bottles in the other experiments. Experiment III (field): To determine the ecological relevance of Experiments i and ii, field experiments were conducted. There were 32 10- X 10-cm plots at the ERA, with each plot containing three sundews (mean diameter 5.07 ± 1.38 cm). To each of four randomly chosen plots was applied one of the following treatments: DI water, acetone (10%), or commercial or technical forms malathion. At the start of the experiment 5 ml of the appropriate insecticide was applied directly to the sundews using spray bottles, and there were two subsequent applications after 10 and 20 days (within the range of recommended application frequency). The field plots were slightly larger in area than the plastic cups used in the lab, and the field rates of application for insecticide a.i./plot were 3.3 kg/ha (2.94 lb a.i./A) for malathion. According to the study authors, the rates of insecticide application used for this experiment represented an overspray scenario for mosquito control, but were comparable to the rates used for control of agricultural pests. Experiment IV (lab): Eight 2-year old Venus flytraps (mean fresh-weight 1.03 ± 0.41 g) were planted in individual 9 cm diameter plastic cups filled to 5 cm with a mixture of 2/3 peat moss and 1/3 perlite. Plants of the same age and similar fresh-weight to minimize variation in trap size. To each plant the following treatments were applied using spray bottles: DI water, acetone (10%), or commercial or technical forms of malathion, using the same concentrations as in Experiment i. There were two subsequent applications of each treatment after 10 and 20 days (within the range of recommended application frequency). For each experiment, there were no statistical differences (p>0.05) between negative and acetone controls, so results were pooled. Survival analyses were conducted using the Cox proportional hazards model in R 2.11., and then conducted multiple comparisons between treatments using log-likelihood ratio tests, controlling for the false discovery rate using the Benjamini-Hochberg correction. The study authors found that pink sundews are more sensitive to malathion exposure than Venus flytraps under field conditions and that the formulated malathion is more toxic than the technical grade under both lab and field conditions. Table 1 presents the results of the study for malathion. Figure 1 presents survival data (copied from paper without review). Table 1. Effects of malathion on pink sundew and Venus flytrap survival.
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