Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
Fluosilicic acid Sulfur dioxide
Potassium permanganate Sulfuric acid
Sodium aluminate Tetrasodium pyrophosphate
Distribution networks constitute another potential source of
chemical contaminants in drinking-water. The materials used in
distribution networks may serve as a pollutant source by leaching into
the water over time. Some examples include lead from lead-containing
solders and pipes, asbestos fibres from the surface of asbestos-cement
pipes and cadmium from metallic fittings. Other contaminants include
PAHs from coal-tar-based sealants, plasticizers, stabilizers and
solvents used in the manufacture of plastic pipes.
Water sources experience considerable variations in quality over
time and geographic location. The quality of river water may change
rapidly during heavy storms, melting snows and droughts. The quality
of water in lakes may be affected by climate, season, location or some
combination thereof. Groundwater historically has enjoyed the most
consistent quality, with relatively constant composition. However, the
vulnerability of groundwater to contamination is gaining widespread
attention, with particular emphasis on synthetic organic substances,
surface impoundments, landfills, agriculture, leaks and spills, land
disposal of wastewater, septic tanks and the petroleum/mining
production industries.
7.3.2 Water quality monitoring strategies
There are numerous considerations in the design of a monitoring
and measurement strategy for water quality assessment. The
International Organization for Standardization (ISO) has provided
guidance on a number of issues related to sampling strategies for
water quality assessment (Table 27). A sound monitoring methodology
must be followed by the appropriate sample storage and transportation,
to minimize changes in sample composition. Losses can occur due to
several physical, chemical and biological changes, such as ion
exchange, adsorption with the container material, oxidation to
precipitated forms, loss of volatiles to the vapour space and
biochemical conversions. For contaminants at low source
concentrations, these changes can introduce significant errors in the
analytical results.
Table 27. ISO standards of water quality giving guidance on sampling
ISO standard Title (water quality)
number
5667-1: 1980 Sampling - Part 1: Guidance on the design of sampling
programmes
5667-2: 1982 Sampling - Part 2: Guidance on sampling techniques
5667-3: 1985 Sampling - Part 3: Guidance on the preservation and
handling of samples
5667-4: 1987 Sampling - Part 4: Guidance on sampling from lakes,
natural and man-made
5667-5: 1985 Sampling - Part 5: Guidance on sampling of
drinking-water and water used for food and beverage
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