National analysis campaign on drug residues in water: results in line with expectations
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News of 10/02/2011
10 February 2011
The presence of emerging substances (1) in the environment at trace levels (2) and particularly that of drug residues in water has in recent years been an issue for public opinion, the scientific community and the public authorities. The health risks associated with these substances are of particular concern.
There is currently no qualitative limit for drug residues in water, and screening for them under European and French regulations is not envisaged.
A national campaign covering a quarter of the population
In this context, and although no studies to date have demonstrated any health risk related to the presence of drug residues in water, the French Ministry of Health wished to investigate the presence of these substances in water intended for human consumption.
In 2006 it therefore began reinforcing screening for these drugs and in September 2009, in collaboration with ANSES’s (3) Nancy Laboratory for Hydrology, it launched a national campaign to measure 45 pharmaceutical substances of human or veterinary origin, or their metabolites (4), based on a list (5) compiled by ANSES and AFSSAPS ((6).
The strategy for selecting sampling sites enabled nearly a quarter of the population to be covered, in both mainland France and its overseas départements. Every département was investigated. Samples were taken from resources used to produce water intended for human consumption (surface and groundwater) and from treated water leaving the purification plant.
This campaign ended in June 2010. The results relate to both raw water (surface or ground water prior to purification treatment) and treated water (7). The final analysis of the results, mainly taking contextual information into account, was released in January 2011.
With regard to raw water, approximately 285 samples were analysed. Two thirds of these samples came from groundwater and one third from surface water. The treated water corresponding to this raw water is distributed to 24% of the population of the entire national territory.
Based on prioritisation work carried out by AFSSAPS and AFSSA in 2008, 45 molecules were screened for in this study. All the main pharmacological classes of drugs are represented.
In about 75% of the treated water samples, whether from ground or surface water, none of these 45 molecules could be quantified (except caffeine which is also a marker of human activity).
For the 25% of samples that were positive, the analyses typically revealed the simultaneous presence of one to four molecules.
Among the 45 molecules investigated, 26 were not found in any of the samples. Nineteen were detected at least once, with five of these being found at concentrations too low to be quantified (8).
Apart from caffeine, the molecules most frequently found were carbamazepine (an anti-epileptic drug) and its main metabolite (9), as well as oxazepam (an anxiolytic) which is both a parent drug and a benzodiazepine metabolite.
Over 90% of samples had a cumulative maximum concentration below 25 ng/L and less than 5% had a cumulative maximum concentration exceeding 100 ng/L.
In raw water, the same three main molecules were found. However, a greater number of substances (30 vs. 19) were identified, at concentrations sometimes higher than in the treated water. The maximum value measured did not exceed 450 ng/L and was found for only one substance. This comparison of raw/treated water therefore seems to illustrate the effectiveness of the treatment processes.
The results of this study also showed that carbamazepine may act as a ‘control’ molecule, testifying to the presence and persistence of drugs in water.
A first approach to risk assessment
Simultaneous to the preparation of this campaign, the Directorate General for Health formally requested that ANSES and AFSSAPS assess the health risks related to the presence of drug residues in water intended for human consumption.
The aim of this risk assessment is to determine the relevance of including or excluding certain molecules in the health control measures for water. The health risk assessment is particularly complex, especially given the low concentrations encountered and the variable biological effects that have to be investigated. The concentrations found in treated water are one thousand to one million times lower than those used in therapeutic doses.
ANSES and AFSSAPS are working to define a general methodology for assessing these risks. An initial document on the assessment of exposure via water was published in June 2010 (10). Work on the overall methodology is ongoing and its application is being tested on carbamazepine, the most frequently found substance. Once the general risk assessment methodology has been consolidated, the assessment will continue on certain other typical molecules, quantified in the water during this campaign, and used in human and/or veterinary medicine.
For the record, the environmental risk related to drug residues is already evaluated by the health agencies as part of their examination of applications for marketing authorisation of medicines for both human and veterinary use, and is a first step in risk reduction.
The plan to control drug residues is the continuation of the work of the 2004-2008 French National Health & Environment Plan (PNSE 1) and is included in the PNSE 2 (2009-2013) among emerging risks and, to a lesser degree, among water contaminants. In this respect, the primary targets are known hazardous substances, particularly polycyclic aliphatic hydrocarbons, nitrates and pesticides, in order to limit the amounts released into the aquatic environment, and disinfection by-products generated when controlling the quality of water supplied.
In this context, an inter-ministerial action plan on drug residues in water, co-led by the Ministries of the Environment and Health, will guide the research in this field. This plan is intended, as a preventive measure, to further reduce discharges into the environment. All the stakeholders have participated in the preparatory work: institutional players, healthcare professionals, academics, researchers, industry, user and patient groups, and environmental protection associations. The action plan is scheduled to be published in the first quarter of 2011.
Find out more
(1) New water pollutants or contaminants
(2) Concentrations of the order of a billionth or a millionth of a gram per litre with regard to drug residues in water
(3) French Agency for Food, Environmental and Occupational Health & Safety
(4) Products of metabolism of the drug in the body
(5) Report entitled "Prioritisation of drug residues of interest for the analysis of resources and treated water"
(6) French Health Products Safety Agency
(7) When leaving the purification plant, i.e. ready for distribution to the consumer's tap
(8) Concentrations below 1 to 50 nanograms per litre (ng/L) depending on the molecule, which corresponds to 1 to 50 billionths of a gram
(10) Report entitled "Drug residues in water intended for human consumption”: Document on "General methodology for assessing human exposure to drug residues via water intended for human consumption"