Page 7: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Formaldehyde

Rationale

A guideline value for formaldehyde in drinking water, based solely on health considerations, can be derived from the TDI as follows:

Figure 2. Tolerable daily intake (TDI) equation

Figure 1

where:

  • 0.15 mg/kg bw per day is the TDI, as derived above
  • 70 kg is the average body weight of an adult
  • 0.05 is the proportion of total daily intake allocated to drinking water (as most of the exposure to formaldehyde is from food [89%, as calculated from data in the "Exposure" section] and less than 2% is from water, an allocation of 5% of the TDI to drinking water is considered appropriate)
  • 1.5 L/d is the average daily consumption of drinking water for an adult.

A health-based guideline value of 0.35 mg/L (350 µg/L) for formaldehyde in drinking water can thus be derived. However, because this concentration is more than 25-fold higher than concentrations normally found in water supplies (1.2-13 µg/L), it is not considered necessary to establish a maximum acceptable concentration (MAC) for formaldehyde in drinking water.

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