The basic and essential requirement in water works is to provide the public with an adequate supply of safe drinking water (World Health Organization [WHO], 2011). Preserving the safe quality of water is vital to sustain life, protect human health, and contribute to social development (Vrba & Lippon, 2007). As the 20th century progressed, the identification of chemical water pollution became more important due to the outbreaks associated with chemical spills or leaks into potable water. In the mid 1970s, an event occurred that led to concern about chemicals in water because of chloroform in finished water treated with chlorine (Calderon, 2000). The Centers for Disease Control and Prevention (CDC) reported 34 waterborne disease outbreaks from 1993 through 2006 in the U.S. related to chemical constituents including nitrate and nitrite, fluoride, and lead (Post, Atherholt, & Cohn, 2011).
Health risk concerns related to chemical contamination of drinking water differ from those related to microbial contamination and arise mainly from the ability of chemical constituents to cause adverse health effects after an extended time of exposure (WHO, 2011). Changes in water quality occur progressively except for those substances that are discharged or leach intermittently to flowing surface waters or groundwater supplies from contaminated landfill sites (WHO, 2011). The problem of chemical contamination in drinking water bodies may cause several health problems. Tooth discoloration and skeletal fluorosis are caused by excessive fluoride intake from drinking water (Maheshwari, 2006; WHO, 2011). A high content of nitrate and nitrite leads to methemoglobinemia in infants less than six months of age and also possible formation of nitroso-compounds that are known to be carcinogens in the digestive system (Manassaram, Backer, & Moll, 2007).
Iron and chloride are also of widespread significance because of their effects on water taste and acceptability (American Public Health Association [APHA], 2012; WHO, 2011). Iron concentration in drinking water above the acceptable limit can be objectionable because it stains laundry and may affect taste (WHO, 2011). Turbidity is a principal physical characteristic of water quality that could provide absorption sites for toxic substances and microorganisms in the water and subsequently protect pathogenic and indicator microorganisms from disinfectants (Edzwald, 2011). Total dissolved solids (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in a given amount of water (APHA, 2012). Reliable data on possible health effects associated with the ingestion of TDS in drinking water are not available (WHO, 2011). The WHO guideline value of 1,000 mg/L for TDS is based on the taste and acceptability rather than health effects. Acceptability may vary according to circumstances. Furthermore, water with extremely low concentrations of TDS may also be unacceptable to consumers because of its flat, insipid taste (WHO, 2011).
Many studies show groundwater pollution from chemicals is a growing problem worldwide that is caused by numerous types of human activities (Babiker, Mohamed, Terao, Kato, & Ohta, 2004; Celik, Unsal, Tufenkci, & Bolat, 2008; Fang & Ding, 2010; Hudak, 2012; Kumar, Kumari, Ramanathan, & Saxena, 2007; Lee, Min, Woo, Kim, & Ahn, 2003; Loni & Raut, 2012; Nas & Berkaty, 2006; Subramani, Elango, & Damodarasamy, 2005). The water quality is highly affected by residential, municipal, commercial, industrial, and agricultural activities (U.S. Environmental Protection Agency, 1993). Deterioration of groundwater quality especially in arid and semiarid areas is a major concern that has been intensified by population growth and increases in demand for food supplies. Decreasing rainfall combined with increased evaporation from increased temperature as a result of climate change will affect groundwater levels in these regions (Wilby et al., 2006). The lack of adequate water resources and access to safe drinking water in arid and semiarid regions cause serious health hazards and expose many people to health risks (Schmoll, 2006). Thus, providing safe drinking water through proper management and monitoring of water resources is vital for the protection of public health and environmental safety.
Iran is an arid/semiarid country with an average precipitation of 251 mm/year (Assadollahi, 2009). The entire renewable water resource in Iran totals 130 billion cubic meters, out of which 92% is used for agriculture, 6% is used for domestic use services, and 2% is used for industrial uses (Assadollahi, 2009). For this reason, our study was designed 1) to assess the quality of water resources in the central part of Iran, which uses water after chlorination and without any additional treatment for drinking; and 2) to evaluate the impact of decreasing rainfall on the quality of some water resources in two successive years.
A total of 65 raw water samples were collected in clean polyethylene bottles between June and November 2012 from different drinking water resources including wells, springs, and aqueducts in Isfahan province. Isfahan province is located in the center of Iran; it has a moderate and dry climate with an average annual temperature of 16.7[degrees]C and an average annual rainfall of 116.9 mm (Assadollahi, 2009). The sampling, preservation, and analysis of water was carried out as recommended by the American Public Health Association (2012).
The turbidity and electrical conductivity (EC) were determined and EC measurements were converted to TDS values by multiplying EC by a factor of 0.55 as recommended for water resources (APHA, 2012). The concentrations of nitrate, nitrite, and fluoride were assayed by DR5000 according to manufacturers' instructions and chloride concentration was determined by the Mohr method. Iron analysis of water samples was carried out using a flame atomic absorption spectrophotometer.
In order to evaluate the effect of...