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Pesticides and water quality in Croatian main capital

The City of Zagreb's public water supply system is the largest water supply system in the Republic of Croatia regarding the number of consumers and the amount of water supplied. The system is divided into 5 supply zones according to the geographical area: Zagreb-South, Zagreb- West, Zagreb-East, Zagreb-North and Zagreb- South-East. Drinking water monitoring is carried out annually in the City of Zagreb and its surroundings in accordance with applicable legislation (Council Directive 98/83/EC and Role book NN 125/17). The purpose of monitoring is to collect data on all parameters defined by the legislation, in order to make an assessment of the compliance of drinking water. Most of the samples included in this monitoring are analysed at the Andrija Štampar Teaching Institute of Public Health, and the obtained results are forwared to the Croatian Institute of Public Health which is responsible for conducting the monitoring. One of the parameters which have to be checked for the determination of the compliance of drinking water is the determination of pesticide residues. Pesticide residues are determined by gas and liquid chromatography techniques with different detection methods (HPLC, UPLC-MS/MS, GC-ECD). As a part of the monitoring for 2019 year, a total of 192 pesticides were determined, of which 2 were from the triazine herbicides group, 18 were from the organochlorine pesticides group and 172 were from the organophosphorus and other pesticides group. All analytical methods applied for the determination of pesticide residues in drinking water have been successfully validated and accredited according to the HRN EN ISO 17025. Also, interlaboratory comparison study were successfully performed ( z score<2). In a year 2019, a total of 133 samples were analysed. In the 48 samples (36%), determined concentration of pesticides (atrazine) were above the limit of quantification (from 0.021 to 0.084 µg L-1), but none of the samples showed the concentartion of pesticides above the Maximum Residue Levels (MRL). The largest percentage of positive water samples is related to supply zone of Zagreb-South (24%) and Zagreb-West (9.7%). The mean value of atrazine in water samples belonging to these zones wERE 0.043 µg L-1 and 0.033 µg L-1, respectively. Although, the presence of atrazine has been established in a quite number of the analysed samples, obtained values are far below the MRL (0.10 µg L-1), and should not indicate risk to human health.

water quality ; pesticides residues ; GC/MS ; LC/MS/MS ; Atrazine

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