Pharmaceuticals and pesticides in rural community drinking waters of Quebec, Canada – a regional study on the susceptibility to source contamination

In Canada, the presence of pharmaceuticals and pesticides in municipal drinking water has been examined primarily in larger urban centres which draw their supplies from surface water. However, few studies have examined this issue in smaller and rural communities, which represent nearly one-third of the Canadian population and which draw their drinking water mainly from groundwater. This study presents a regional-scale assessment of the presence of these contaminants in the drinking waters of 17 smaller rural communities, compared with two larger urban communities, in south-central Quebec. From a total of 70 chemicals examined, 15 compounds (nine pharmaceuticals and six pesticides) were detected. The three most frequently detected contaminants were caffeine, atrazine and naproxen, respectively, in 29%, 24% and 21% of the samples. Detections reported here for the first time in Quebec drinking water include the known human carcinogen cyclophosphamide and the fungicide thiabendazole. Maximum concentrations of pharmaceuticals ranged from 30 to 1,848 ng L 1 and of pesticides from 21 to 856 ng L . This study provides direct evidence that drinking water in smaller, rural communities of Quebec, Canada, whether sourced from groundwater or surface water, can contain measurable levels of pharmaceuticals and pesticides, indicative of their susceptibility to source contamination. doi: 10.2166/wqrj.2019.038 om https://iwaponline.com/wqrj/article-pdf/54/2/88/555109/wqrjc0540088.pdf er 2019 Barry Husk (corresponding author) Juan Sebastian Sanchez BlueLeaf Inc., 310 Chapleau Street, Drummondville, Quebec J2B 5E9, Canada E-mail: bhusk@blue-leaf.ca Juan Sebastian Sanchez Roland Leduc Olivier Savary Hubert Cabana Faculty of Engineering, Department of Civil Engineering, Université de Sherbrooke, 2500 Boulevard de l’Université, Sherbrooke, Quebec J1K 2R1, Canada Larissa Takser Faculty of Medicine, Department of Obstetrics and Gynecology, Université de Sherbrooke, 3001 12e Avenue Nord, Sherbrooke, Quebec J1H 5N4, Canada


INTRODUCTION Anthropogenic contaminants in drinking water
Sources of drinking water are increasingly subjected to a wide range of trace organic contaminants of anthropogenic origin. Aided by improved analytical methods, such contaminants are now commonly detected in aquatic environments in many countries, including Canada. They are found in both surface water and groundwater (Segura The presence of such trace organic contaminants in aquatic environments is of concern both due to their potential impact on aquatic ecosystems, where sub-lethal effects have been found in aquatic organisms at environmentally relevant concentrations (Brausch et  Nearly a third of the Canadian population, some 12 million people, use groundwater for drinking water, and over 80% of the Canadian rural population depends on groundwater for its entire water supply (Environment & Climate Change Canada ). In the province of Quebec, Canada, groundwater enables water supply to nearly 90% of inhabited territory, supplying about 20% of the population, including over 700 municipal drinking water distribution networks, making it the Canadian province with the most municipalities in this situation (Nowlan ). Approximately 25% of these Quebec municipal groundwater supply networks apply no treatment to the drinking water before its distribution (MDDELCC ).
Rural areas differ from most urban areas in that they source drinking water primarily from groundwater. Consequently, with few exceptions (e.g., Benotti et al. ; Kozuskanich et al. ), the majority of studies of treated municipal drinking water systems have, by implication, examined surface water systems which are the primary source of drinking water in larger urban environments.
However, anthropogenic contaminants, including human pharmaceuticals, are known to contaminate natural aquatic environments in rural areas with lower population densities (Nebot et al. ) and groundwater contamination by rural septic system effluents has been recognized as a potential health concern (Withers et al. ). Also, due to the concentration of agricultural activities in rural areas, these less populous regions are disproportionately at greater risk of exposure to pesticide contamination through drinking water (Hallberg ; Starner & Goh ; Sultana et al. ). In addition, in some jurisdictions, regulatory requirements for drinking water testing frequency and number of parameters are less demanding for smaller municipalities, including in this study region where municipalities of less than 5,000 people have lower such requirements due to the cost of analyses (Gouvernement du Québec ). This essentially creates a two-tier system of drinking water supply, split roughly along an urban/rural divide, and potentially places populations of smaller rural municipalities at higher risk than those of larger urban municipalities where regulatory requirements are more stringent (Hrudey et al.

Research gaps and challenges
As a preventative measure, public health and environmental authorities in Canada are requiring drinking water suppliers to examine the vulnerability of their sources of drinking water to contamination from anthropogenic pollutants (Government of Ontario ; Government of Quebec ). However, in spite of the regulatory measures put in place, gaps persist in reaching a full understanding of the vulnerability of treated drinking water to the presence of trace organic contaminants in many parts of Canada, particularly in rural communities using groundwater supplies. Some of those gaps and research challenges include the following: • Determining sufficient frequency and duration of sampling in order to permit the evaluation of temporal variations. • Emphasizing regional versus local studies, in order to capture land use, geological and other variables over wider areas.
• Conducting simultaneous sampling of all sites within regional studies to permit accurate temporal comparison between sites.
• Selecting which compounds to analyse from the vast number of potential contaminants, including both regulated and non-regulated contaminants, as well as their degradation by-products and metabolites.
• Achieving acceptable analytical limits of detection (LD) for targeted compounds.
As a result of these combined challenges, there is a limited evidence base available to policymakers, drinking water regulators, suppliers and consumers to enable a better understanding of the presence and susceptibility of treated drinking water to contamination by trace organic contaminants, especially in smaller, rural communities, including in Quebec, Canada. Taking these situations into account, this study was structured to respond to as many of these research gaps and challenges as possible, while examining the presence of markers of anthropogenic contamination in rural community drinking waters of south-central Quebec.

Choice of contaminant compounds
While drinking water supplies may be contaminated by trace organic contaminants from a multitude of sources, in order to undertake efficient prevention and remediation programmes it is essential to identify the primary sources of contamination in any particular watershed. To aid in that process, we have identified and structured our search around two major sources of pollutants of anthropogenic origin found in aquatic environments, particularly in rural areas: (a) agricultural products and (b) human wastewater from septic or municipal wastewater effluent.
In order to evaluate exposure of drinking water sources to these two categories of contaminants, a select group of products representative of each category have been chosen in this study as 'markers' (or 'proxies') of the presence of that category. Detection of such markers would thereby indicate the vulnerability of source water exposure to contaminants of that origin, as well as the potential for the presence of other products from the same category. Typically, as markers representative of potential agricultural contamination in drinking water, agronomic pesticides are chosen (Ongley ; Snow et al. ), and in the case of potential contamination by human wastewater, pharmaceuticals are commonly used (Lim et al. ). Contaminants from both categories were included in this study so as to permit a greater understanding by individual municipalities of specific sources of pollutants susceptible to being found in their region.
The choice of individual compounds selected for analysis is outlined in Table 1. This selection was based on a combination of the volumes of pesticides used in Quebec and the volumes of pharmaceuticals consumed in Canada, as well as the analytical method used and analytical standards available. Products of various sub-categories were included while ensuring that they could be analysed simultaneously according to the multi-residue analytical techniques employed.

Study area and site selection
In order to examine the presence of anthropogenic trace organic contaminants in drinking water supplies on a regional scale, a series of 17 municipalities sourcing their drinking water from groundwater in the south-central region of Quebec was selected. In addition, for comparison purposes, two municipalities sourcing their drinking water from surface water were included, for a total of 19. This  Table 2.

Sampling methods
The study was conducted in two stages, the first in one rural community sourcing its drinking water from individual private groundwater wells (St-François-Xavier-de-Brompton, 'SFXB'), over two years (2013)(2014), every two weeks between May and November, for a total of 26 campaigns. The second stage was conducted on a regional scale in 16 additional rural communities sourcing their municipal drinking water from groundwater, as well as two larger municipalities (Sherbrooke and Drummondville) sourcing their drinking water from surface water. Sampling for this second stage was carried out monthly over two years (2014)(2015), between May and November, for a total of 12 campaigns. The December to April period was excluded from sampling of both stages for logistical reasons. Discrete (grab) samples were water was allowed to run from the taps for 2 to 3 min before collecting the sample. The water samples were transported on ice and stored the same day at 4 C in the dark until sample preparation and analysis, according to standard sampling procedures (MDDEP ; CEAEQ ).

Analytical methods
The analytical methods for pharmaceuticals and pesticides used in this project were performed according to Ba et al. Both calibration curves were performed in triplicate.
The recovery was between 90% and 110% (data not shown).

Detections, quantifications and concentrations
Of the 70 compounds evaluated in 314 samples, 15 products (nine pharmaceuticals and six pesticides) were detected in at least one sample over the three-year period of the study.  Table 3, indicating the number of detections and quantifications, the frequency of detection, as well as the maximum concentrations detected per molecule, and are compared to the Quebec regulatory drinking water standards (also Appendix, Figure A1, available with the online version of this paper  (Table 4).

Temporal variation
The results of monthly temporal variation as determined by the number of detections per sample, per month, per molecule, are illustrated in Table 4 (also Appendix, Figure A2, available online). Temporal presence of pesticides per sample increased steadily from May until peaking in August and September, followed by a downward trend in

Sources of contaminants by municipality
In many jurisdictions, including this study region, municipalities are required to evaluate potential risks to public drinking water supplies from sources of anthropogenic contamination (Government of Ontario ; MDDELCC ).
Moreover, the World Health Organization recommends that municipalities implement water safety plans (WSPs), a comprehensive approach for risk assessment and risk management of drinking water (World Health Organization ). However, many of these studies do not examine sources of contaminants or do not include anthropogenic contaminants.
In this study, we have categorized contaminants according to their source, either from human waste  Significant differences exist between the two surface water-sourced municipalities, both in terms of source of water as well as treatment methods (Table 2 and Appendix, These results illustrate how such analysis could assist municipal water resource managers in the determination of sources of anthropogenic contamination for each municipality and in their water sanitation programmes. It is also an indication that private groundwater wells can be equally or more affected by these contaminants than municipal drinking water sources.

Potential human health issues and concerns
While human health issues are not the primary focus of this study, it is important to place the findings of this study in the  In addition to the findings in this study, pharmaceuticals are frequently detected in treated drinking water elsewhere (Benotti et al. ; Daughton ). In this study, the finding of cyclophosphamide, detected in 49 samples, or 16%, is of particular concern. Cyclophosphamide is a medication used as chemotherapy and to suppress the immune system.
It is a known human carcinogen and is a cytotoxic, genotoxic, anti-neoplastic drug, even at low concentrations (Zounková et al. ). It was detected repeatedly and consistently in five out of seven months of the May to November period of this study, in multiple municipalities, confirming its regular presence in these drinking waters. Based on 1.5 L day À1 of adult water consumption, exposure to this chemical could exceed the suggested 1,500 ng person À1 day À1 threshold of toxicological concern (Kroes et al. ). An additional potential concern with such cytotoxic drugs is the possibility that carcinogenic effects could exist at any level of exposure (i.e., there is no threshold dose below which no carcinogenic effects may occur). Of particular concern are any special subgroup populations which may be more vulnerable to developmental concerns, such as pregnant women, their fetuses and breast-fed infants (Johnson et al. ; Rowney et al. ). Therefore, when considering potential indirect exposure via drinking water supplies, the use of a benchmark based on therapeutic dose may not be applicable to any pharmaceuticals that may be non-threshold genotoxins (Webb et al. ). Also detected at high concentrations is mefenamic acid, a member of the nonsteroidal anti-inflammatory class of drugs (NSAIDs) and which is used to treat mild to moderate pain.
The results of our study also indicate that drinking water in this region is a vector of exposure to complex mixtures of chemicals, with as many as 13 separate compounds of the 70 tested being detected in individual samples (Appendix, All drinking water treatment plants in this study use chlorine-based disinfection methods which are subject to the unintentional production of disinfection by-products. Although not evaluated in this study, the presence of these by-products is a growing health concern due to their acknowledged carcinogenic/ genotoxic potential (Richardson et al. ).

CONCLUSIONS AND RECOMMENDATIONS
This study examined the presence of markers for two cat-