Water testing for some pesticides and herbicides in the UK are required to have a detection limit in Parts Per Trillion - PPT. The EPA of America recommends water testing for some contaminants to be set at 70 parts per trillion.

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This UK research paper states:

"Pesticides are well known potential contaminants of drinking water supplies. As such water companies are required to screen water for contamination of pesticide classes such as organophosphate, organonitrogen, triazins, carbamates, acid herbicides and phenol urea pesticides. The required lower limit of quantitation for these pesticides is usually 100 ppt with a detection limit of 20 ppt and a CV of analysis of ideally 12% or below at the limit of detection."

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In New Zealand, testing for 1080 poison residues is set with a limit of detection of 1 part per billion, despite that The Ministry of Health has stated there have been no epidemiological studies carried out with regard to 1080 and potential adverse health effects on people.

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Water testing for the presence of 1080 poison is not often undertaken. Most New Zealand testing is initiated 24 hours or more after an aerial operation - when the poison has been up-taken by aquatic life and plant life and diluted or passed through the water column - and when detection is unlikely. The negative results are then pooled and used to inform the public that 1080 poison is rarely detected in the water. It is like the police testing drunk-drivers 24 hours or more after their consumption of alcohol and then pooling the negative results to claim that alcohol is rarely detected in motorists, and therefore breath-testing is not warranted.

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In this letter, a Health Board representative explains their reasons for testing at 24 hours or later.