Pesticides concentration levels

It must be demonstrated that a high and repeatable recovery percentage is attainable from all samples at several pesticide concentration levels. 

Pesticide Concentration Levels. The purpose of this experiment was... 

Pesticide Concentration Levels. As anticipated, a linear relation-... 

Today, when a pesticide with no detectable residues is registered for use, a Tolerance or maximum residue limit (MRL) is established at the lowest concentration level at which the method was validated. However, for risk assessment purposes it would be wrong to use this number in calculating the risk posed to humans by exposure to the pesticide from the consumption of the food product. This would be assuming that the amount of the pesticide present in all food products treated with the pesticide and for which no detectable residues were found is just less than the lowest level of method validation (LLMV). The assumption is wrong, but there is no better way of performing a risk assessment calculation unless the limit of detection (LOD) and limit of quantification (LOQ) of the method were clearly defined in a uniformly acceptable manner. 

If analytical methods are validated in inter-laboratory validation studies, documentation should follow the requirements of the harmonized protocol of lUPAC. " However, multi-matrix/multi-residue methods are applicable to hundreds of pesticides in dozens of commodities and have to be validated at several concentration levels. Any complete documentation of validation results is impossible in that case. Some performance characteristics, e.g., the specificity of analyte detection, an appropriate calibration range and sufficient detection sensitivity, are prerequisites for the determination of acceptable trueness and precision and their publication is less important. The LOD and LOQ depend on special instmmentation, analysts involved, time, batches of chemicals, etc., and cannot easily be reproduced. Therefore, these characteristics are less important. A practical, frequently applied alternative is the publication only of trueness (most often in terms of recovery) and precision for each analyte at each level. No consensus seems to exist as to whether these analyte-parameter sets should be documented, e.g., separately for each commodity or accumulated for all experiments done with the same analyte. In the latter case, the applicability of methods with regard to commodities can be documented in separate tables without performance characteristics. 

More than 80% of Moldavia s bodies of water in 1985-86 were dangerously contaminated with pesticides. The level of pesticide contamination was high in the main rivers of Ukraine the concentrations of DDT and its metabolites in the Dnepr reached 0.384 mkg/l [23]. 

Comparing the six sampling points monitored in this study (Fig. 4), HEIMD followed by HDAD were the most polluted ones, showing concentration levels of total pesticides above 5 pg/L in 39% and 22% of the samples analyzed, respectively. As expected, the sampling points located in the two bays (HEM and HDM) were the less polluted, due to the dilution effect of the marine water. This dilution effect may explain also the higher contamination level observed in the northern bay as compared to the southern bay, which is comparatively larger in size and depth. 

In several AT studies, pesticide levels in the Ebro were found to be high. Hildebrandt et al. [50] found a homogeneous contamination pattern from atrazine (and also from simazine from May 2000) in intensive Rioja cultivation areas throughout the Ebro. Nearer to the delta, Barata et al. [72] found high levels of bentazone, methyl-4-chlorophenoxyacetic acid, propanil, molinate and fenitrothion in water, while Kuster et al. [71] found low concentration levels of atrazine and simazine at the delta, but high levels of other pesticides used in rice cultivation. Importantly, Hildebrandt et al. [50] found that levels of pesticides in groundwater... 

Fig. 2.6. Chromatogram showing the simultaneous analysis of 16 PAHs (A), 7 chlorobenzenes (B), 10 organochlorine pesticides (C), and 7 PCBs (D). Column RapidMS (10 ml x 530 jim i.d., 0.12 pm df, Varian, The Netherlands. GC oven 50°C (lmin) to 190°C (3 min) at 30°C/min to 280°C at 40°C/min. MS time-selected SIM mode with dual ion confirmation. Analyte concentration levels were between 50 and 175 ppb [38].

Exposure Levels in Humans. Metabolism of endrin in humans is relatively rapid compared with other organochlorine pesticides. Thus, levels in human blood and tissue may not be reliable estimates of exposure except after very high occupational exposures or acute poisonings (Runhaar et al. 1985). Endrin was not found in adipose tissue samples of the general U.S. population (Stanley 1986), or in adipose breast tissue from breast cancer patients in the United States (Djordjevic et al. 1994). Endrin has been detected in the milk of lactating women (Alawi et al. 1992 Bordet et al. 1993 Dewailly et al. 1993), but no data from the United States could be located. Data on the concentrations of endrin in breast milk from U.S. women would be useful. No information was found on levels of endrin, endrin aldehyde, or endrin ketone in blood and other tissues of people near hazardous waste sites. This information is necessary for assessing the need to conduct health studies on these populations. 

In the Ebro river zone (NE Spain), pesticide concentrations in groundwater were much higher than in the Llobregar river area. Hildebrandt et al. [18, 19] found in groundwater samples collected in 2000-2001 very high levels of metolachlor (10-2000 ng/L) and triazines (2460, 1980, 1270, 790 and 540 ng/L for atrazine, DEA, terbuthylazine, DIA and simazine, respectively). However, 3 years later (2004), triazines concentrations decreased dramatically, whereas metolachlor presented levels even higher (from 2,000 to 5,370 ng/L). 

Another example of the potential pernicious effects of pesticides upon human health is the study conducted at the University of Colorado where researchers have found that higher concentrations of four pesticides - atrazine, simazine, alachlor and metolachlor - in groundwater are significantly associated with higher levels of Parkinson disease. For every 10 pg/L increase of pesticide levels in the drinking water, they found that the risk for Parkinson disease increased by 3% and their water samples had pesticide concentrations ranging from 0.0005 to 20 pg/L [38]. 

Even though the number of pesticides surveyed amounted to more than 100, only 46 were actually detected (Table V). From records that were kept as well as unidentified GLC peaks, other pesticides were deposited Into the beds but either were not detected by the gas chromatography procedure, were present In undetectable levels or were unknown or unregistered compounds. Tables VI to XI show the average accumulated pesticide concentrations from each of the six field stations having the heaviest use of the evaporation beds. 

Table I presents the change in concentration of each pesticide as a function of time at the three initial levels of 20 mg/L, 60 mg/L and 100 mg/L. The theoretical pesticide concentration is also shown in Table I as calculated from Equation 4 with k = 1, which assumes complete pesticide removal in one pass. The data are graphed and presented in Figure 5 as tank concentration versus time.

LC techniques are widely diffused for the determination of hydrophilic but not volatile and thermally unstable pesticides. Since the European Community Directive [68] indicates 0.1 pg L" as the concentration threshold level for a single pesticide in waters destined for human consumption, to quantify these concentration levels, suitable pre-concentration and extraction procedures must be generally performed prior to the HPLC determination. The extraction methods are based on LLE, MAE, on-line continuous flow liquid membrane extraction (CFLME), and mainly on SPE and SPME. Many SPE procedures are used the packing materials are graphitized carbon, ODS, styrene-divinylbenzene co-polymers, or selective phases based on immunoafflnity. The extraction can be performed on- and off-line, manually, or in a semi-automated way. 

Figure 16.13 illustrates the pesticides responsible for the nonuniformity of the rejected samples. Thanks to the implementation of control in the country of origin of the plant, and information given to the farmers (selective and rational use of pesticides), it was possible to lower the pesticide concentrations to safe levels. 

Most active principles and pharmaceutical forms are processed in the presence of organic solvents or reagents. The current regulations on products generally restrict to a few p.p.m. the amount of residual solvent. This very low concentration level could favour the CO2 utilization when non-polar compounds have to be eliminated. On the other hand, the elimination of residual solvents from tablets, films or other pharmaceutical preparations in which organic solvent are involved has been addressed [15]. Another application is related to the removal of residues from medical materials such as monomers, additives or polymerization residues from polymers or elastomers. Purification of active principles includes elimination of other undesired molecules pesticides from some vegetal extracts, and antibacterials suspected of toxic co-extracts from natural sources. 

The first chlordane-related mortality was of three wild birds and was recorded between 1978 and 1981 (Blus et al., 1983). The levels of chlordanes and heptachlor epoxide from the two adult male red-shouldered hawks (Buteo lineatus) and an adult female great horned owl (Bubo virginianus) were within the critical lethal range that has been defined by experimental studies (heptachlor epoxide in brain tissue 3.4-8.3 pg g-1 wet wt. oxychlordane in brain tissue 1.1 5.0 pg g-1 wet wt.). The chlordane poisoning of birds has been reported in several studies in the United States (Blus et al., 1983, 1985 Post, 1951 Stansley Roscoe, 1999). From 1986 to 1990, 122 cases of avian mortality due to chlordane and/or dieldrin were documented in New York, Maryland and New Jersey (Okoniewski Novesky, 1993). High pesticide concentrations were found in cyclodiene-resistant insect populations. These pesticide-tainted insects, when eaten by birds, caused mortalities in the avian populations (Okoniewski Novesky, 1993). 

Figure 10.3. Average (white bar) concentration levels of organochlorine pesticides contaminated in marine organisms from Eastern coast of the gulf of Thailand comparing to Extraneous residue Limit (ERL). (Source Kan-atireklap et al., 2002.)...

Table 14.2 summarizes available data on selected POP contamination in water in Malaysia. DDTs were found in most rivers in Malaysia but the concentration levels varied from region to region with centrally located rivers being detected to be highly contaminated. Surprisingly, DDTs concentration increased in these rivers as compared to rivers from other parts of the country even after DDT was banned from use in 1999. End-osulfans were not detected in most rivers in the 1989 survey but were found at relatively high concentrations in later studies (Table 14.2). Concentrations of other pesticides in river waters have also been reported in these studies. In the earlier study (Tan et al., 1991), aldrin, dieldrin, end-rin, and heptachlor were also found in some of the rivers. The concentration levels were ND-0.5 ng L-1 for aldrin, ND-0.3 ng L-1 for dieldrin, ND-3.2ng L-1 for endrin, and 0.3-3.4 ng L-1 for heptachlor. Our study...

The other study on human cord blood collected in a Kuala Lumpur hospital (Benjamin Tan and Mustafa, 2003) reported that only chlopyrifos was found in 18% of the samples at levels of ND-1.15ng mL-1 while other pesticides analyzed, such as lindane, diazinon, endrin, and endosulfans were not detected. In the same study, bisphenol-A and nonylphenols were detected in more than 80% of the samples at concentration levels of ND-4.05 and ND-15.17ng mL-1, respectively. Several alkylphenols were also found in these blood samples. 

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