Health risk assessment related to water quality and microcystin contamination of water in the Kuibyshev Reservoir was conducted in August 2012 during the period of algal bloom. The health risk during recreational activity was estimated for potential exposure to extracellular microcystins. Microcystin content in water measured by the indirect competitive ELISA method was in the range from 0.21 to 26.96 μg L−1. The results of the present study show that the health risk can reach a dangerous level even at 1 h of exposure due to the high concentration of extracellular microcystins in the water.

INTRODUCTION

Eutrophication, as a result of agricultural, industrial and urban activity, is a ubiquitous problem (Pelaez et al. 2010). In the Asia Pacific Region 54% of lakes are eutrophic; the proportions for Europe, Africa, North America and South America are 53%, 28%, 48% and 41%, respectively (Bartram et al. 1999). Eutrophication has led to an increase in the formation of harmful cyanobacterial algal blooms. Some cyanobacterial species/strains can produce a wide range of secondary metabolites with toxic properties, including neurotoxins, hepatotoxins, dermatotoxins, and irritant toxins (Carmichael 1992; Codd et al. 2005). These toxins can exert harmful effects on aquatic communities, lead to death of livestock, wild and domestic animals, as well as lead to some human health problems (Ueno et al. 1996; Fitzgerald 2001; Vasconcelos 2001; Stewart et al. 2006). Worldwide about 60% of cyanobacterial samples investigated contain toxins (World Health Organization (WHO) 2003). The problem of cyanotoxin contamination is real for Russia too (Lower Suzdalskoeskoe Lake (Voloshko et al. 2010), Lake Ladoga (Voloshko et al. 2008), Lake Nero (Babanazarova et al. 2011), Lake Kotokel (Belykh et al. 2011), etc.), including the reservoirs of the Volga-Kama cascade (Sidelev et al. 2013).

Microcystins are the most frequently occurring and widespread cyanotoxins (Sivonen & Jones 1999). They are cyclic heptapeptides containing a specific amino acid (ADDA) and act by blocking protein phosphatases (PP1 and PP2A) causing toxicity at the hepatic level; moreover, cumulative damage may occur (Zaccaroni & Scaravelli 2008). Microcystins have been well documented as produced by strains and species of Anabaena, Anabaenopsis, Aphanizomenon, Aphanocapsa, Cylindrospermopsis, Lyngbya, Microcystis, Nostoc, Oscillatoria, Phormidum, Planktothrix, Rivularia and Synechococcus but most frequently by Anabaena as well as by Microcystis (Sivonen & Jones 1999; Rastogi et al. 2014). One cell of Microcystis may contain about 0.2 pg of microcystin (Codd et al. 2005).

Mass developments and especially surface scums of blue-green algae pose a risk. Cyanotoxins can be taken up by humans orally and through inhalation or through skin contact during recreational activity. Various exposure scenarios include swimming, fishing, boating, water-skiing, and canoeing. For microcystins, swimming is a key factor (Butler et al. 2012).

For toxic effects other than carcinogenesis, there is generally considered to be a ‘threshold dose’ that can be tolerated without toxic effects to the organism. Thresholds exist because the body has mechanisms to prevent harm from many outside chemicals and because of biological redundancy. The concept of a tolerated dose is the basis of most health-based regulatory concentration limits for non-carcinogenic effects (Butler et al. 2012). The maximum tolerated dose, also called reference dose, is determined on the basis of the hazardous substance concentration in water. According to the World Health Organization recommendations, microcystin concentration in drinking water may not exceed 1 μg L−1 (World Health Organization (WHO) 2011). Unfortunately, in many countries, including Russia, there are no standards for microcystins in recreational waters. In the framework of the Regional Program of Water Safety for Human Health the screening of the presence of cyanotoxins in water during the period of intensive algal bloom was carried out.

The aim of the study was to measure the level of extracellular microcystins in the surface water of Kuibyshev Reservoir during the period of harmful algal bloom and to assess the health risk during recreational activity for potential exposure to extracellular microcystins in comparison with the health risk posed by background chemical content in the water.

MATERIALS AND METHODS

The study area and sampling sites

The Kuibyshev Reservoir is situated in the Russian Federation, in the Middle Volga and Lower Kama region (Figure 1). It was created in 1955–1957 by the dam of the Zhiguli Hydroelectric Station on the Volga River near Zhigulyovsk and Tolyatti in Samara Oblast. It is the largest reservoir in Europe and the third largest in the world. The reservoir has a surface area of 5,900 km² and a volume of 57.3 km3; about 16% of the reservoir is shallow (less than 3 m depth). The reservoir is located within five regions in Russia: Republic of Tatarstan (50.7%), Ulyanovsk (30.9%) and Samara (14.7%) oblasts, and the Chuvash and Mari republics (3.7%) (Rozenberg & Vikchristyuk 2008). The Kuibyshev Reservoir is a multi-purpose water body; it is important for drinking and industrial water supply, energy generation, mining, fire safety, transportation, agriculture, fishing, forestry, recreation, etc. As a result the reservoir has a sufficiently high level of pollution by heavy metals, petroleum hydrocarbons, nitrogen, phosphorus compounds, etc.

Figure 1

Study region and location of the sampling sites in the Kuibyshev Reservoir; and zones of external total phosphorus (P) and nitrogen (N) load (kg km–2 year–1) to the reservoir (Petrov, 2004, from Rozenberg & Vikchristyuk (2008)).

Figure 1

Study region and location of the sampling sites in the Kuibyshev Reservoir; and zones of external total phosphorus (P) and nitrogen (N) load (kg km–2 year–1) to the reservoir (Petrov, 2004, from Rozenberg & Vikchristyuk (2008)).

The study region was located within the Republic of Tatarstan and included 19 stations of the shallow (depth ≤3 m) and deep water zones (Table 1) of three ecological regions: in the Volzhskii reach of the upper part, in the Volzhsko-Kamskii reach of the water formation zone downstream of the Volga and Kama confluence and in the Tetyushinskii reach of the middle part of the reservoir. Sampling sites were chosen according to territory division on the basis of external total nitrogen and phosphorus load from all sources (Rozenberg & Vikchristyuk 2008) to the reservoir (Figure 1).

Table 1

Sampling site locations in the Kuibyshev Reservoir and their description

Geographic coordinates
SiteLatitude, NLongitude, EDescription of siteDepth, m
55 °49′42″ 48 °22′04″ Near the Kozlovka settlement 11 
55 °49′17″ 48 °24′45″ 3 km upstream of Zelenodolsk 
55 °46′21″ 48 °40′15″ The mouth of the Sviyaga River (right tributary) 
55 °47′23″ 48 °59′27″ 1 km above the water intake of Kazan 13 
55 °47′50″ 49 °04′39″ The mouth of the Kazanka River (left tributary) 
55 °42′30″ 49 °00′27″ 5 km downstream from Kazan 18 
55 °29′42″ 49 °03′26″ Near the Kyzyl Bayrak settlement 15 
55 °23′44″ 49 °02′49″ Near the Burtasy settlement 
55 °23′49″ 49 °03′10″ Near the Burtasy settlement 
10 55 °17′49″ 49 °25′15″ Near the Makarovka settlement 
11 55 °16′50″ 49 °26′38″ Near the Makarovka settlement 
12 55 °16′20″ 49 °15′43″ The water area of Volzhsko-Kamsky Biosphere Reserve 
13 55 °16′11″ 49 °16′22″ The water area of Volzhsko-Kamsky Biosphere Reserve ∼2 
14 55 °12′44″ 49 °17′16″ Near the Kamskoye Ustye settlement 12 
15 55 °08′48″ 49 °09′41″ Near the Kirelskoe settlement 
16 55 °05′34″ 49 °07′30″ Near the Sukeevo settlement 12 
17 54 °59′14″ 49 °03′05″ Near the Bolgar town 
18 54 °51′33″ 48 °53′52″ Near the Tetushii town 
19 54 °51′21″ 48 °54′29″ Near the Tetushii town 
Geographic coordinates
SiteLatitude, NLongitude, EDescription of siteDepth, m
55 °49′42″ 48 °22′04″ Near the Kozlovka settlement 11 
55 °49′17″ 48 °24′45″ 3 km upstream of Zelenodolsk 
55 °46′21″ 48 °40′15″ The mouth of the Sviyaga River (right tributary) 
55 °47′23″ 48 °59′27″ 1 km above the water intake of Kazan 13 
55 °47′50″ 49 °04′39″ The mouth of the Kazanka River (left tributary) 
55 °42′30″ 49 °00′27″ 5 km downstream from Kazan 18 
55 °29′42″ 49 °03′26″ Near the Kyzyl Bayrak settlement 15 
55 °23′44″ 49 °02′49″ Near the Burtasy settlement 
55 °23′49″ 49 °03′10″ Near the Burtasy settlement 
10 55 °17′49″ 49 °25′15″ Near the Makarovka settlement 
11 55 °16′50″ 49 °26′38″ Near the Makarovka settlement 
12 55 °16′20″ 49 °15′43″ The water area of Volzhsko-Kamsky Biosphere Reserve 
13 55 °16′11″ 49 °16′22″ The water area of Volzhsko-Kamsky Biosphere Reserve ∼2 
14 55 °12′44″ 49 °17′16″ Near the Kamskoye Ustye settlement 12 
15 55 °08′48″ 49 °09′41″ Near the Kirelskoe settlement 
16 55 °05′34″ 49 °07′30″ Near the Sukeevo settlement 12 
17 54 °59′14″ 49 °03′05″ Near the Bolgar town 
18 54 °51′33″ 48 °53′52″ Near the Tetushii town 
19 54 °51′21″ 48 °54′29″ Near the Tetushii town 

According to the Tatarstan Republic state report (MENR RT 2013), in August 2012 cyanobacteria dominated almost everywhere in the reservoir, ranging from 60% to 100% of the total phytoplankton abundance and from 47% to 100% of the total phytoplankton biomass. The highest phytoplankton biomass was observed in the expanded zone of the reservoir near the Kamskoye Ustye settlement. Bloom regions of water were composed almost only of blue-green algal species Anabaena flos-aquae, Aphanizomenon flos-aquae, and Microcystis aeruginosa. The abundance of phytoplankton in areas of algal blooms reached 25 × 1012 cells and biomass 1.7 kg/m3.

Water sample collection and field analysis

Observations were performed on 10–14 August 2012, during the mass development of blue-green algae. Water samples were collected at a depth of 0.1–0.2 m from the surface layer of water in 1.5 L containers and were stored refrigerated at 5 °C before analyses (up to 5 days). The geographic coordinates of sampling sites were recorded using a global positioning system by a GPSMAP-178C (Garmin, Olathe, USA).

Measurements of the trophic-related physicochemical parameters, including depth, Secchi depth, pH, temperature, and dissolved oxygen were carried out in the field. Depth was determined using a boat echo sounder GPSMAP-178C, Secchi depth was determined using a 30 cm white Secchi disk, pH was measured by a portable pH-meter/ionometer Anion-7051 (Infraspak-Analyte, Novosibirsk, Russia), temperature and dissolved oxygen concentration were measured by a portable oxygen meter Mark-303 (Vzor, Nizhny Novgorod, Russia).

Laboratory studies

For quantitative microcystin analysis, water samples were filtered through cellulose filter paper (2.5 μm pore size). The extracellular microcystin concentration in filtrate was determined with an enzyme-linked immunosorbent assay by a commercial microplate Microcystins-ADDA ELISA kit PN 520011 (Abraxis, Warminster, USA). The test is an indirect competitive ELISA method for the congener-independent detection of microcystins. It is based on the recognition of microcystins and their congeners by specific antibodies with a color reaction. The color was evaluated using a Uniplan microplate reader (Pikion, Moscow, Russia) at 450 nm wavelength according to the manufacturer's instructions.

Health risk assessment

Human health risk was assessed according to Guideline 2.1.10.1920–04 (2004). To assess potential human exposure to cyanotoxins and other substances, ingestion during swimming as the main recreational exposure scenario was considered. Swimmers may unconsciously ingest water while swimming. Cyanotoxins in the swallowed water can be absorbed into the blood from the stomach and intestines. The absorbed dose (ADDi, μg kg−1 day−1) is calculated using the following equation: 
formula
1
where Cw is cyanotoxin concentration in water, IR is ingestion rate (0.05 L h−1), ET is exposure time (h/event), 1 h in this study, usually the time spent swimming is greater (2–3 h), and BW is bodyweight of the exposed individual (adult is 70 kg, child is 15 kg).
The International Agency for Research on Cancer (IARC) classifies the risk of microcystin-LR as a possible carcinogen (World Health Organization (WHO) 2011). However, it is considered that microcystins are dangerous primarily due to the development of non-neoplastic liver lesions (Butler et al. 2012). The index of the risk (HQi) of non-cancerous diseases from exposure to the pollutant is calculated using the following equation: 
formula
2
where RfD is a reference dose (μg kg−1 day−1), which for microcystins is 0.0064 (Butler et al. 2012). For non-carcinogenic effects the scale of ecological risk includes five levels of risk: HQi <0.1 – minimal; 0.1 < HQi ≤1 – low; 1 < HQi ≤5 – moderate; 5 < HQi ≤10 – high; HQi >10 – dangerous (Guideline 2.1.10.1920–04 2004).

As the next step, we compared the level of health risk related to cyanotoxin exposure with the risk from background chemical content in the water of the Kuibyshev Reservoir (from Muhametshina et al. 2013). The risk was calculated from the ingestion of substances with water using the same exposure parameters as the cyanotoxins. Values for RfD were taken from Guideline 2.1.10.1920–04 (2004) and Integrated Risk Information System (IRIS, www.epa.gov/iris).

Statistical analysis

Statistical analysis was performed by using Statistica 8.0 (StatSoft, Tulsa, USA) and the data were expressed as mean or mean ± standard error. Differences among samples were evaluated using the non-parametric Mann–Whitney U-test and Kruskal–Wallis analysis of variance (non-parametric ANOVA). Correlations between parameters were evaluated using Spearman's rank order correlation coefficient. Differences were considered statistically significant at P ≤ 0.05. A hierarchical cluster analysis was carried out using the single-linkage clustering method applying Euclidean distance as the distance or similarity measure to determine the zones of cyanotoxin contamination.

RESULTS AND DISCUSSION

The average microcystin concentrations and ranges of the physicochemical parameters of the water are presented in Table 2. The average water temperature (24.5 ± 0.3 °C) was conducive for mass development of blue-green algae. Dissolved oxygen concentration and pH ranged from 7.1 to 14.6 mg L−1 and from 8.4 to 9.9, respectively. Generally, these parameters increase with active photosynthesis. The Secchi depth (1.1 ± 0.1 m) indicated the process of eutrophication (Carlson 1977).

Table 2

Mean concentration of microcystins (MC), Secchi depth (SD), water temperature (T), pH, and dissolved oxygen concentration (DO) in the water samples

SiteMC (μg L−1)SD (m)T (°C)pHDO (mg L−1)
5.86 ± 0.17 0.9 24.7 9.1 10.8 
3.34 ± 0.33 1.9 23.7 8.8 8.4 
0.45 ± 0.02 0.7 23.2 8.6 8.5 
8.28 ± 0.46 1.4 26.2 9.1 11.1 
1.14 ± 0.13 0.8 24.8 9.3 14.6 
1.25 ± 0.31 1.3 23.7 8.8 9.8 
0.65 ± 0.13 1.3 23.7 8.9 10.1 
20.86 ± 0.41 0.1 26.7 9.9 14.6 
22.97 ± 0.70 0.1 26.7 9.9 14.6 
10 2.83 ± 0.24 n/a 24.2 8.6 8.1 
11 0.54 ± 0.08 1.7 23.3 8.5 8.3 
12 0.44 ± 0.13 1.5 23.9 8.4 7.45 
13 0.28 ± 0.05 n/a n/a n/a n/a 
14 26.96 ± 2.50 1.3 24.7 9.5 11.3 
15 0.21 ± 0.03 1.2 24.1 8.7 7.1 
16 2.41 ± 0.24 1.0 24.8 9.0 11.3 
17 1.13 ± 0.32 0.5 24.5 8.6 9.5 
18 2.15 ± 0.36 n/a n/a n/a n/a 
19 2.01 ± 0.06 1.5 23.1 8.5 8.14 
SiteMC (μg L−1)SD (m)T (°C)pHDO (mg L−1)
5.86 ± 0.17 0.9 24.7 9.1 10.8 
3.34 ± 0.33 1.9 23.7 8.8 8.4 
0.45 ± 0.02 0.7 23.2 8.6 8.5 
8.28 ± 0.46 1.4 26.2 9.1 11.1 
1.14 ± 0.13 0.8 24.8 9.3 14.6 
1.25 ± 0.31 1.3 23.7 8.8 9.8 
0.65 ± 0.13 1.3 23.7 8.9 10.1 
20.86 ± 0.41 0.1 26.7 9.9 14.6 
22.97 ± 0.70 0.1 26.7 9.9 14.6 
10 2.83 ± 0.24 n/a 24.2 8.6 8.1 
11 0.54 ± 0.08 1.7 23.3 8.5 8.3 
12 0.44 ± 0.13 1.5 23.9 8.4 7.45 
13 0.28 ± 0.05 n/a n/a n/a n/a 
14 26.96 ± 2.50 1.3 24.7 9.5 11.3 
15 0.21 ± 0.03 1.2 24.1 8.7 7.1 
16 2.41 ± 0.24 1.0 24.8 9.0 11.3 
17 1.13 ± 0.32 0.5 24.5 8.6 9.5 
18 2.15 ± 0.36 n/a n/a n/a n/a 
19 2.01 ± 0.06 1.5 23.1 8.5 8.14 

n/a = not analyzed.

The extracellular concentrations of microcystins ranged from 0.21 to 26.96 μg L−1. The highest concentration was found in an algal bloom area in the expanded zone of the reservoir at sampling site 14. In the littoral zones (sampling sites 8 and 9) algal scum had formed crust, and high microcystin concentrations were found as well. The microcystin concentration in superficial waters of Kuibyshev Reservoir is comparable with concentrations detected in surface waters from other countries (Italy, from non-detectable values up to 226.16 μg L−1, Messineo et al. 2009; Mexico, 4.9–78.0 μg L−1, Vasconcelos et al. 2010; Vietnam 0.91–46 μg L−1, Duong et al. 2014; and others). As is known from the literature (Misson et al. 2012; Quiblier et al. 2013), toxins produced by cyanobacteria can be found not only in planktonic freshwater cyanobacteria but in benthic as well. Thus, we plan to assess the contribution of benthic cyanobacteria to the total amount of microcystins in future research.

Concentrations of cyanotoxins at 12 sampling sites exceeded the guideline values of 1.0 μg L−1 in drinking water as determined by the WHO, both in shallow and in deep water zones. The Mann–Whitney U-test revealed no statistically significant differences between samples taken in the shallow and deep water zones (P = 0.744). Furthermore, Kruskal–Wallis analysis of variance revealed no statistically significant differences between microcystin concentrations in samples taken in different ecological regions of the reservoir (P = 0.381). Probably, this is due to wind and wave action providing intensive horizontal and vertical mixing of water masses. Some authors (Sivonen & Jones 1999) indicate the influence of this factor on distribution of microcystins in water.

Cluster analysis revealed the distribution of cyanotoxin content on the basis of ‘external total phosphorus (P) and nitrogen (N) load (kg km–2 year–1)’ (Figure 2): 1 – high level of cyanotoxins and high level of phosphorus (P) and nitrogen (N) load; 2 – moderate level of cyanotoxins, moderate level of nitrogen (N) and high level of phosphorus (P); 3 – moderate level of cyanotoxins and moderate level of phosphorus (P) and nitrogen (N) load.

Figure 2

Distribution of cyanotoxin content on the basis of ‘external total phosphorus (P) and nitrogen (N) load (kg km–2 year–1)’.

Figure 2

Distribution of cyanotoxin content on the basis of ‘external total phosphorus (P) and nitrogen (N) load (kg km–2 year–1)’.

The physicochemical parameters and microcystin concentrations were analyzed for potential statistical relationships (Table 3). As expected, there was positive correlation with temperature (R = 0.620), pH (R = 0.730) and the dissolved oxygen (R = 0.648), because intensive photosynthesis may lead to supersaturation of dissolved oxygen and high pH levels in the water column.

Table 3

Spearman's correlation matrix between microcystin concentration and measured physicochemical parameters

ParametersMC (μg L−1)H (m)SD (m)T (°C)pHDO (mg L−1)
MC (μg L−11.000         
H (m) –0.050 1.000     
SD (m) –0.198 0.171 1.000       
T (°C) 0.620 –0.156 0.569 1.000     
рН 0.730 0.126 0.529 0.796 1.000   
DO (mg L−10.648 0.219 0.596 0.736 0.896 1.000 
ParametersMC (μg L−1)H (m)SD (m)T (°C)pHDO (mg L−1)
MC (μg L−11.000         
H (m) –0.050 1.000     
SD (m) –0.198 0.171 1.000       
T (°C) 0.620 –0.156 0.569 1.000     
рН 0.730 0.126 0.529 0.796 1.000   
DO (mg L−10.648 0.219 0.596 0.736 0.896 1.000 

Marked correlations are significant at P < 0.05.

It is considered that water transparency is closely correlated to abundance of algae (Carlson 1977); therefore, it can be related to the concentration of cyanotoxins. In this study, the Secchi disk transparency has a low negative correlation with the microcystins. The microcystins could be found in high concentrations in the absence of blue-green algae and could be found in small concentrations in the mass development of cyanobacteria. Thus, the cyanotoxin concentrations in the waters did not always correlate with the cyanobacteria cell densities, as Messineo et al. (2009) already observed in Italian freshwaters. As a result, some cyanotoxin indication techniques based on counting algal cells may lead to wrong conclusions (Butler et al. 2012). For the correct description of the hazard, it is necessary to directly measure toxins in water.

To assess the potential influence of cyanotoxins on human health, we calculated the values of health risk (Table 4). It was shown that risk level ranged between 0.02 (low) and 14.04 (dangerous). The estimated risk level was 4.7 times higher for children than for adults.

Table 4

Human health risk assessment related to microcystins in the Kuibyshev Reservoir

SiteAdults
Children
ADDi (μg kg−1 day−1)HQiRisk levelADDi (μg kg−1 day−1)HQiRisk level
0.0042 0.65 Low 0.0195 3.05 Moderate 
0.0024 0.37 Low 0.0111 1.74 Moderate 
0.0003 0.05 Minimal 0.0015 0.23 Low 
0.0059 0.92 Low 0.0276 4.31 Moderate 
0.0008 0.13 Low 0.0038 0.59 Low 
0.0009 0.14 Low 0.0042 0.65 Low 
0.0005 0.07 Minimal 0.0022 0.34 Low 
0.0149 2.33 Moderate 0.0695 10.86 Dangerous 
0.0164 2.56 Moderate 0.0766 11.96 Dangerous 
10 0.0020 0.32 Low 0.0094 1.47 Moderate 
11 0.0004 0.06 Minimal 0.0018 0.28 Low 
12 0.0003 0.05 Minimal 0.0015 0.23 Low 
13 0.0002 0.03 Minimal 0.0009 0.15 Low 
14 0.0193 3.01 Moderate 0.0899 14.04 Dangerous 
15 0.0002 0.02 Minimal 0.0007 0.11 Low 
16 0.0017 0.27 Low 0.0080 1.26 Moderate 
17 0.0008 0.13 Low 0.0038 0.59 Low 
18 0.0015 0.24 Low 0.0072 1.12 Moderate 
19 0.0014 0.22 Low 0.0067 1.05 Moderate 
SiteAdults
Children
ADDi (μg kg−1 day−1)HQiRisk levelADDi (μg kg−1 day−1)HQiRisk level
0.0042 0.65 Low 0.0195 3.05 Moderate 
0.0024 0.37 Low 0.0111 1.74 Moderate 
0.0003 0.05 Minimal 0.0015 0.23 Low 
0.0059 0.92 Low 0.0276 4.31 Moderate 
0.0008 0.13 Low 0.0038 0.59 Low 
0.0009 0.14 Low 0.0042 0.65 Low 
0.0005 0.07 Minimal 0.0022 0.34 Low 
0.0149 2.33 Moderate 0.0695 10.86 Dangerous 
0.0164 2.56 Moderate 0.0766 11.96 Dangerous 
10 0.0020 0.32 Low 0.0094 1.47 Moderate 
11 0.0004 0.06 Minimal 0.0018 0.28 Low 
12 0.0003 0.05 Minimal 0.0015 0.23 Low 
13 0.0002 0.03 Minimal 0.0009 0.15 Low 
14 0.0193 3.01 Moderate 0.0899 14.04 Dangerous 
15 0.0002 0.02 Minimal 0.0007 0.11 Low 
16 0.0017 0.27 Low 0.0080 1.26 Moderate 
17 0.0008 0.13 Low 0.0038 0.59 Low 
18 0.0015 0.24 Low 0.0072 1.12 Moderate 
19 0.0014 0.22 Low 0.0067 1.05 Moderate 

The risk level for background chemical concentrations in the Kuibyshev Reservoir in 2012 are presented in Table 5. The cumulative risk corresponds to the minimum level (HQi = 0.014 for adults and HQi = 0.066 for children), with the largest contribution of total petroleum hydrocarbons. Comparison of both risks shows that the health risk related to cyanotoxins was up to 212 times greater. To sum up, dangerous levels of risk pose a real threat to human health. This highlights the need to implement mandatory cyanotoxin control in recreational water resources.

Table 5

Human (adults) health risk assessment related to natural background concentrations of main pollutants (from Muhametshina et al. 2013) in the Kuibyshev Reservoir in 2012

SubstanceConcentration (mg L−1)MAC (mg L−1) (Russia)RfD (μg kg−1 day−1)ADDi (μg kg−1 day−1)HQi
Cd 0.0004 0.005 0.5 0.0003 0.00057 
Cr (VI) 0.013 0.02 0.0093 0.00310 
Co 0.04 0.01 20 0.0286 0.00143 
Cu 0.006 0.001 19 0.0043 0.00023 
Fe 0.24 0.1 300 0.1714 0.00057 
Mn 0.11 0.01 140 0.0786 0.00056 
Mo 0.001 0.001 0.0007 0.00014 
Ni 0.028 0.01 20 0.0200 0.00100 
NH4+ 0.40 0.5 980 0.2862 0.00029 
NO3 3.01 40.0 1600 2.1510 0.00134 
NO2 0.05 0.08 100 0.0352 0.00035 
PO43– 0.11 0.20 – – – 
Zn 0.03 0.01 300 0.0214 0.00007 
Total petroleum hydrocarbons 0.19 0.5 30 0.1357 0.00452 
Phenol 0.002 0.001 300 0.0014 0.00001 
Total:      0.01418 
SubstanceConcentration (mg L−1)MAC (mg L−1) (Russia)RfD (μg kg−1 day−1)ADDi (μg kg−1 day−1)HQi
Cd 0.0004 0.005 0.5 0.0003 0.00057 
Cr (VI) 0.013 0.02 0.0093 0.00310 
Co 0.04 0.01 20 0.0286 0.00143 
Cu 0.006 0.001 19 0.0043 0.00023 
Fe 0.24 0.1 300 0.1714 0.00057 
Mn 0.11 0.01 140 0.0786 0.00056 
Mo 0.001 0.001 0.0007 0.00014 
Ni 0.028 0.01 20 0.0200 0.00100 
NH4+ 0.40 0.5 980 0.2862 0.00029 
NO3 3.01 40.0 1600 2.1510 0.00134 
NO2 0.05 0.08 100 0.0352 0.00035 
PO43– 0.11 0.20 – – – 
Zn 0.03 0.01 300 0.0214 0.00007 
Total petroleum hydrocarbons 0.19 0.5 30 0.1357 0.00452 
Phenol 0.002 0.001 300 0.0014 0.00001 
Total:      0.01418 

Marked concentrations exceed Russian maximum allowable concentration (MAC).

CONCLUSIONS

This study is one of the few in Russia dedicated to quantitative cyanotoxin estimation in surface waters with emphasis on human health risk. It has been demonstrated that a risk to human health caused by cyanotoxins exists. Taking into account that the ratio of extracellular cyanotoxin content in water to the total amount can range from 0.003% to 10%–20% (Sivonen & Jones 1999; Messineo et al. 2009), the risk posed by the extracellular toxins may underestimate the total risk as it doesn't account for intracellular toxins.

The next step of the investigation will concern the total cyanotoxin content including extra- and intracellular amounts. The results of this study will be useful for improvement of surface water monitoring in water supply and recreation zones.

ACKNOWLEDGEMENTS

The authors would like to thank the editor and anonymous reviewer for their constructive comments, which helped to improve the manuscript. This work was funded by the subsidy allocated to Kazan Federal University for state assignment in the sphere of scientific activities.

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