Pesticides sampling frequency

Fig. 2 Boxplots of the concentrations of individual and total pesticides and frequency of detection (expressed in % in parentheses) in the water samples collected from each of the six sampling sites. HDAD, HDCD, HEOD, and HEIMD draining channels HDM and HEM bays DIA Deisopro-pylatrazine DEA desethylatrazine...

The lymphocytes from 31 patients exposed to various organophosphate pesticides were examined for chromosomal aberrations (Van Bao et al. 1974). Five of the patients were exposed to methyl parathion only. Blood samples were taken 3-6 days after exposure and again at 30 and 180 days. A significant (p<0.05) increase was noted in the frequency of stable chromosomal aberrations in acutely intoxicated persons (although such cells are eventually lost from the cell population). Two of the methyl parathion-exposed persons had taken large doses orally in suicide attempts. The study limitations include small sample size, absence of a control group, lack of quantification of exposure levels, and possible... 

As explained in Section 5.2.3, p,p -DDE is much more persistent in food chains than either p,p -DDT or p,p -DDD, and dnring the 1960s when DDT was still extensively used, it was often the most abundant of the three compounds in birds and mammals found or sampled in the field. Since the widespread banning of DDT, very little of the pesticides has been released into the environment, and p,p -DDE is by far the most abnndant DDT residue found in biota. While discussing the ecological effects of DDT and related compounds, effects on population numbers will be considered before those on popnlation genetics (gene frequencies). 

In our opinion, the fact that republics where a very large amount of pesticides were used, such as Azerbaijan, Tajikistan, and Turkmenistan, all were reported to be those with the most favorable levels of pesticide content in food indicates the data were falsified. It is also surprising that, according to official data, in Moldavia only 9% of samples containing pesticides had levels exceeding MPLs. At the same time, the frequency of pesticides being detected in food products grew from year to year, and from 1983-87 made up 3.99%, 5.59% 5.79% 8.93% and 7.96% of the studied samples [1]. 

The frequency of multiple residues in the three datasets analyzed by Baker et al. is shown in Table 14.1. The PDP found that about 45% of conventional fruit and vegetable samples tested from 1994-1999 contained residues of two or more pesticides, while 7.1% of organic samples had multiple residues. The average conventional apple tested in this period by PDP contained residues of three different pesticides. In CU testing 62% of conventional samples contained multiple residues, compared to 6% of organic samples. 

Mirex residues were detected in food samples analyzed as part of the FDA Pesticide Residue Monitoring Studies conducted from 1978--1982 of 49,877 food samples and from 1982-1986 of 49,055 food samples however, the frequency of detection was unspecified but was <1 and 2% respectively (Yess et al. 1991a, 1991b). A similar 1985 analysis of foods grown in Ontario, Canada, failed to detect any mirex or photomirex in any of the vegetable, fruit, milk, egg, or meat products tested (Davies 1988). Mirex was also detected in the FDA Pesticide Residue Monitoring Study from 1986-1987 however, the frequency of detection was unspecified but less than 1% (FDA 1988). 

In the Monte Carlo analysis samples are drawn at random from the residue distribution and then from the apple consumption distribution to provide the data points for the intake distribution. This sequence is repeated several thousand times until a smooth intake distribution curve is produced. The intake distribution shown in Fig. 2.5 represents 20,000 samples drawn from the pesticide residues and apple consumption distributions shown in Figs 2.3 and 2.4. The bars represent the relative frequency of each intake level and the line is the cumulative frequency distribution. The distribution is very skewed and it can be seen that the cumulative frequency is nearing 100% when only the mid-point of the distribution is being approached. This means that very high intakes are relatively rare occurrences. 

While these data represent mere snapshots of the global situation, they ofier a stark warning. Given that the use of such toxic pesticides is widespread, evidence of contamination found at one location points to a potential far greater problem worldwide. Furthermore, the few studies which have analysed the frequency of cottonseed contamination have found pesticide residues to be widespread. A recent analysis of cottonseed samples harvested in 5 locations in India found 26 % to be contaminated with chlorpyrifos (WHO II), 22% with endo-sulfan (WHO II),and 16% with ethion (WHO II) . While a parallel study conducted in Pakistan found almost 75% of cottonseed samples to be contaminated with pesticides, with 41% exceeding the prescribed maximum residue limits . According to a recent study conducted by researchers in India, Because of the injudicious and indiscriminate use of insecticides, it is feared that cotton reaching the market may be heavily contaminated with insecticide residues. ... 

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