{'fraction_non_alphanumeric': 0.03796060991105464, 'fraction_numerical': 0.007306226175349428, 'mean_word_length': 5.354187689202825, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Inorganic contaminants in Canadian First Nation community water systems

While previous Canadian studies have examined microbiological water quality in First Nations, there is little published information on inorganic contaminants. In Atlantic Canada, the lead, manganese, and arsenic content of First Nations’ drinking water has been measured for more than a decade, but the data have not been analyzed comprehensively. These contaminants are linked with health problems, and high levels in drinking water are a cause for concern. We examined 12 years of data from 47 First Nation community water systems to identify systems experiencing difficulties meeting sampling frequency or regulatory guidelines. While most contaminant concentrations were below guideline values, we identified elevated concentrations and issues with sampling frequency. No system met both sampling frequency requirements – a minimum of one sample per year per analyte – and regulatory guidelines. Exceedance rates for lead, manganese, and arsenic were high in some systems. Moreover, current sampling procedures for lead specify that taps be flushed prior to sampling, which is known to underestimate lead exposure. We find that a switch to random daytime sampling would at least sometimes yield higher estimates of lead at the tap. Our analysis demonstrates the need for increased monitoring and updated sampling procedures to better characterize inorganic contaminant occurrence in First Nations.


GRAPHICAL ABSTRACT INTRODUCTION
First Nations across Canada have experienced more boil water advisories than municipal communities, due in part to low chlorine residuals, high turbidity, poor infrastructure, and positive coliform samples (Neegan Burnside ; Health Canada a). The federal government has made a commitment to end long-term drinking water advisories by 2021 (Indigenous Services Canada ). Turbidity, chlorine residual, total coliforms, and E. coli counts have been prioritized because boil water advisories are commonly issued as a result of changes in these parameters. Lead, manganese, and arsenic sometimes also exceed the relevant maximum acceptable concentrations or aesthetic objectives specified by Health Canada's water quality guidelines (Health Canada , a, b). But while compliance with microbiological guidelines (e.g., E. coli and total coliforms) and other basic water quality standards (e.g., chlorine residual and turbidity) has been evaluated in previous studies (Neegan Burnside ; Health Canada a), inorganic contaminants have not been analyzed comprehensively; past government reports have provided some data but little analysis (Health Canada a).
Elevated concentrations of arsenic, manganese, or lead may represent a significant public health hazard. Arsenic exposure via drinking water is associated with cardiovascular, reproductive, and neurological effects as well as tumorigenesis (Abdul et al. ). Chronic arsenic exposure through drinking water has been linked with elevated lung cancer mortality (Chiu et al. ). Arsenic may induce neurobehavioral changes (Tsai et al. ), increase fetal mortality, and increase the likelihood of a preterm birth (Hopenhayn et al. ). Health Canada's guidance specifies a maximum acceptable concentration for arsenic of 10 μg/L (Health Canada ).
In the past, manganese was viewed as an aesthetic con- While the previous guideline specified that lead should not exceed 10 μg/L, this may not have been protective as an exposure threshold: for instance, Levallois et al. () found that the odds of blood lead levels at or above the 75th percentile were 4.7 times greater when the mean water concentration was more than 3.3 μg/L.  Between January and August 2018, samples in each of the four community systems were collected from households for the determination of total manganese, lead, and arsenic.

MATERIALS AND METHODS
A water monitor visited each home during working hours, avoiding periods of high-water use and overnight stagnation.
Samples were collected immediately after entry, without a   The water monitor guidelines suggest that guideline exceedances be followed by resampling (Health Canada ). Of the three parameters, arsenic was sampled most frequently, particularly in systems 3, 16, 30, and 45.

RESULTS AND DISCUSSION
System 16 collected 29 or more samples for arsenic every year over the study period. Manganese was sampled, on average, 20 times more frequently than recommended in system 35. Lead was sampled more frequently, on average, than the guideline requirements in 33 systems. System 8 is  the year and included both cold-water and warm-water conditions, we assumed that temperature was not a major factor in our analysis. However, it cannot be ruled out as a potential confounder.
In general, manganese and arsenic levels in random daytime samples were not significantly different from those in flushed samples, with two exceptions. In system 21, arsenic levels were significantly greater in flushed samples, but overall levels were lowat most, 1 μg/Land the difference estimate was not practically significant. In system 35, manganese concentrations were greater in flushed samples by a factor of more than four (Table 2). Manganese levels are strongly seasonal in this water system, with peak levels occurring between August and October. Random daytime samples were collected in June and would, therefore, have missed the seasonal manganese peak.
Comparisons of arsenic and manganese concentrations between random daytime and flushed sampling should be interpreted with care, as seasonality may be an important consideration. Health Canada (b) recommends that sampling for manganese be conducted quarterly throughout the year and weekly when manganese is most likely to be elevated. In lakes, this may be during summer thermal stratification and fall turnover. Health Canada (b) also recommends that groundwater sources be monitored semiannually and that all wells in a well field be monitored; there may be large variation in manganese concentrations among wells in close proximity.

Implications for First Nation sampling policies
Indigenous water systems face unique challenges in delivering safe drinking water, and despite targeted programs to