Abstract The purpose of this analysis is to investigate the effect of application of propoxur (a carbamate insecticide) on the American cockroach. From experimental observations, it has been concluded that the amount of propoxur needed to kill 50% of the test subjects (referred to as LD50) was 0. 0487(%w/v) which deduces to be 0. 22012mg per cockroach (calculated for 0. 452grams of cockroach). The conclusions were drawn immobilising the American cockroach with ice then applying propoxur to be incubated at 23 degrees Celsius. Literature findings in the past were sourced and results were compared with the current study.
Abstract The purpose of this analysis is to investigate the effect of application of propoxur (a carbamate insecticide) on the American cockroach. From experimental observations, it has been concluded that the amount of propoxur needed to kill 50% of the test subjects (referred to as LD50) was 0. 0487(%w/v) which deduces to be 0. 22012mg per cockroach (calculated for 0. 452grams of cockroach). The conclusions were drawn immobilising the American cockroach with ice then applying propoxur to be incubated at 23 degrees Celsius. Literature findings in the past were sourced and results were compared with the current study.
Toxicology of Propoxur introduction introduction Figure 1: Chemical structure of Propoxur Figure 1: Chemical structure of Propoxur The American cockroach (Periplaneta Americana) or more commonly identified as the waterbug is the largest species of the common cockroach. It is considered to be a peri domestic pest and is common in tropical habitats. The P. Americana particularly common in Southern United States and has spread worldwide including Greece, India and Taiwan especially in the subtropics and tropics. The P. Americana is reddish, brown in appearance and an adult grow up to 4cm in length.
Its habitat encompasses warm, humid and shady habitats and can live on average 4 to 21 months. The American Cockroach (as with other pests) is mainly controlled with the use of insecticides. In the current analysis, Propoxur a carbamate insecticide was employed. Carbamate insecticides are derivatives of carbamic acid with the chemical formula of HOC(O)NH2 and elicit paralytic effects on the nervous system with its anticholinesterase action resulting in death. Propoxur appears to be highly effective with cockroaches that display a resistance to organophosphates.
Lethal dose 50 (LD50) is a standard measure of toxicology which represents a dose expressed in milligrams (mg) per kilogram (kg) of mass to kill half (50%) of the test subjects. In acute and chronic toxicity the test subjects are exposed to the insecticide and the lower the LD50 the greater the substances’ toxicity. According to relative toxicity substances may be categorised by comparing LD50 levels. materials and methodologyy materials and methodologyy Please refer to the Pharmacology 1 – Range Finding 1 (Page 21) for a complete listing of materials and detailed procedures. Calculations:
Propoxur (purity) = 97. 6% (this was the sample provided) Therefore for an initial stock solution of 25 ml, 1% w/v, amount of Propoxur (97. 6% pure) weighed was 0. 2561 g. (0. 25/0. 976 = 0. 2561) REsults REsults Table 1: Class results (Group 5/6) Cockroach deaths results as per concentration of propoxur ( % w/v). Control| 0. 005| 0. 01| 0. 02| 0. 05| 0. 1| 0| 0| 1| 3| 5| 5| 0| 4| 4| 5| 5| 5| 0| 0| 0| 2| 3| 5| 0| 0| 3| 2| 3| 5| 0| 0| 1| 2| 4| 4| 0| 0| 1| 2| 5| 5| 0| 0| 0| 2| 3| 4| 0| 0| 1| 1| 4| 5| 0| 0| 0| 0| 3| 5| 0| 0| 0| 1| 3| 5| 0| 0| 1| 1| 3| 5| 0| 0| 2| 1| 4| 5| 0| 0| 1| 2| 4| 5| 0| 0| 1| 1| 4| 5|
Data of groups 5/6 were given and tabulated in given approach. From the data given we were able to construct table 3 where the Mean Mortality, Mortality Percentage and Probit were calculated. Table 2: Group results of cockroach deaths results as per concentration of propoxur ( % w/v). Group B3A| Control| 0. 01%| 0. 01%| 0. 02%| 0. 05%| 0. 10%| Sample 1| 0| 0| 1| 1| 3| 5| Sample 2| 0| 0| 2| 1| 4| 5| Table 3: Compiled Data and Analysis of class results. Concentration| Total Number| Mean Mortality| Mortality (%)| Probit| Control| 5| 0| 0| 0| 0. 005| 5| 0. 29| 5| 3. 36| 0. 01| 5| 1. 14| 22| 4. 23| 0. 02| 5| 1. 79| 35| 4.
61| 0. 05| 5| 3. 79| 75| 5. 67| 0. 1| 5| 4. 86| 97| 7. 75| Tabulated statistical data from the values obtained from Table 1. Probit was calculated to construct Graphs 1 and 2 thus a linear relationship can be formed and LD50 calculated. Graph 1: Comparison between Class Mortality results and Group Mortality. Graph 2: Probit Mortality rate (percent) plotted against concentrations of propoxur ( % w/v). Results were obtained and a probit regression analysis was constructed. From this, statistical data is used to determine the LD50 as per Concentration. P-Values were also determined with 95% Confidence Intervals.
Regression Table Standard Variable Coef Error Z P Constant 3. 18658 1. 32789 2. 40 0. 016 Concentration 1. 14102 0. 420894 2. 71 0. 007 P-Values for the concentration are statistically significant 0. 007<0. 05 Standard 95. 0% Fiducial CI Percent Percentile Error Lower Upper 40 0. 0339977 0. 0113948 0. 0084255 0. 0650006 50 0. 0444242 0. 0138535 0. 0168594 0. 0996456 60 0. 0567346 0. 0179853 0. 0273054 0. 171467 Percentile range represented with 95% Confidence intervals y = 57. 35x + 2. 5017 where; y= Probit x= Concentration Therefore LD50 Propoxur (or Probit 5. 0) for American nymph cockroach is; 5.
0=57. 35x+2. 2017 x=0. 0487 (% w/v) Since LD50 = 0. 0487 grams per 100g (given 100mL=100g) Then, 0. 00022012 grams per 0. 452 grams (weight of one cockroach). Which is, 0. 22012mg per 0. 452 grams (weight of one cockroach). Discussion Discussion “Control of cockroaches relies mainly on the use of synthetic chemicals” (Agrawal et al. 2010). The chemical selected for analysis was the insecticide propoxur and previously has demonstrated to be highly effective in the control if cockroaches. In this experiment Individual groups within the class were formed and carried out the experiment.
The collective data was tabulated as Table 1 and distributed. The data provided the mortality rates per concentration carried out by each group, thus a collective Mean Mortality and Mortality Percentage was calculated and represented in Table 2. This allowed us to transform the Percentages to Probits in which a relationship of concentration to Probits can be graphically represented in a regression form. “Probit Analysis is a type of regression used with binomial response variables and is the preferred statistical method in understanding dose-response relationships (Vincent, 2008).
Using the Probit analysis within the program Minitab allowed us to observe the relationship between the Concentration of propoxur and mortality of the cockroaches. Graph 1 represents the individual group data in comparison to the collective class data. As observed the regression fit is not identical, however demonstrates similarity in terms of cockroach mortality. Graph 2 provides us with the significant statistical data to measure the LD50 whereby observing the median value of the graph we are given a result of 0.
044 (% m/v) for 50% probit. Further calculation allowed us to determine that the mg required for LD50 of the cockroaches 0. 22012mg per 0. 452 grams (weight of one cockroach). Many variables during the experiment may have impacted results. Factors such as handling the cockroaches may have contributed to the incidence of mortality whereby removal of limbs and squashing may have occurred during handling. Incorrect manufacture of dilutions may have also been a significant determent thus the range of error may have been compromised.
The application of the propoxur was also of significance, as a precise measurement was required to be applied to the abdomen of each cockroach of 1 µL. The size and weight of the cockroaches also proved to be of great variance. The average weight of the cockroaches was calculated however some were significantly larger than others and this could potentially alter statistical significance by forming outliers. An improvement of the experiment would be able to provide all cockroaches within the same weight range to increase statistical accuracy, also male or female genus species may also provide a significant observation.
LD50 determination allows for an accurate determination of an effective dose ( to achieve 99% mortality or as required) to be calculated from a smaller sample size and requires less test subjects and therefore is more efficient and cost effective to the industry (Pai, Wu et al. 2005). A previous study conducted by Agrawal et al. demonstrated “propoxur was more effective in reducing the cockroach density by first week in comparison to imidacloprid and fipronil gels but its efficacy started declining after 8th week”. This provides us with significant evidence of the efficiency of the pesticide in comparison to other pesticides.
Also, further studies have shown that human adults have been able to ingest doses of up to 90 mg of propoxur without apparent symptoms (Gosselin et al. 1984). This allows us to assume there is significance in the context of safety. To conclude Propoxur is a commercially available pescticide known as baygon and significant studies have demonstrated its effectiveness, reliability and safety for use in the public. The LD50 values were successfully calculated to which 0. 22012mg of pesticide is required for 0. 452 grams of weighed cockroach.
Although a number of limitations existed within the experimental process they allow for discussion and improvement of experimental procedures. Overall the experiment was a success and provides a result that can be utilised in the public spectrum for pesticide utilisation and safety. References References Pai, H. H. , S. C. Wu, et al. (2005). “Insecticide resistance in German cockroaches (Blattella germanica) from hospitals and households in Taiwan. ” International Journal of Environmental Health Research 15(1): 33-40. Wang, Y. H. , T. Cang, et al. (2012). “Comparative acute toxicity of twenty-four insecticides to earthworm, Eisenia fetida.
” Ecotoxicology and Environmental Safety 79: 122-128. Probit Analysis, Kim Vincent 2008 San Fransico State University, accessed 16/4/2013http://userwww. sfsu. edu/efc/classes/biol710/probit/ProbitAnalysis. pdf Agrawal, V. K. , Agarwal, A. , Choudhary, V. , Singh, R. , Ahmed, N. , Sharma, M. , Narula, K. & Agrawal, P. 2010, ‘Efficacy of imidacloprid and fipronil gels over synthetic pyrethroid and propoxur aerosols in control of German cockroaches (Dictyoptera: Blatellidae)’, J Vector Borne Dis, vol. 47, no. 1, pp. 39-44. Rang, H. P. and M. M. Dale (2012). RANG and DALE’S.