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Description of ache Codex It will be apparent that the body of the Codex is a series of individual monographs, each dealing with a specific compound. Each such monograph contains the following information: Chemical name--alternative acceptable names Chemical abstract service number Chemical formula and formula weight Physical properties a. Function b. Use range Purity requirements Bulk sampling procedures Analytical procedures a. Sample preparation--special procedures are noted where appropriate. In cases where the chemical added is not soluble in water, the analytical procedures apply to a leachate of that material as obtained under the conditions described. Sample analysis--techniques are given either as citations of existing recognized procedures or as procedures developed specifically for the monograph. Purity Requirements The committee recognizes that the assignment of purity requirements depends on the toxicity of the contaminant and the use patterns of the additive. m e interpretation of toxicological data is at times con- troversial and depends on an evolving science. However, the toxicological data base for water impurities is im proving steadily. 2

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3 In arriving at its recommended contaminant limits, the committee met with the Environmental Protection Agency (EPA) to arrive at a list of priority chemicals--those that are used in largest quantities in the public water supply (Table 1). m is list was then categorized accord- ing to use pattern, i.e., those used in (a) coagulation and flocculation; (b) softening, precipitation, and pH control; (c) disinfection and oxidation; and (d) mis- cellaneous treatment applications. In drafting the monographs in each category, a subgroup of the committee reviewed current data on known impurities in the chem- icals, grade of manufactured products, use patterns, and other variables. The committee also developed a list of impurities to be considered. m e list was identical to the regulated inorganic impurities specified by the National Interim Drinking Water Regulations developed in response to the Safe Drinking Water Act of 1974 (Table 2).~ This list was subsequently modified to include those substances for which there is evidence of occurrence as contaminants in water treatment chemicals. The toxicology subgroup of the committee supplied toxicological data on these sub- TABLE 1 Water Treatment Chemicals Included in this Codex Activated alumina Aluminum sulfate Ammonia Ammonium hydroxide Bentonite clay Calcium hydroxide Calcium hypochlorite Calcium oxide Carbon, activated, granular, and powder Carbon dioxide Chlorine Ferric chloride Ferric sulfate Ferrous sulfate Fluosilicic acid Potasium permanganate Sodium aluminate Sodium bicarbonate Sodium calcium magnesium polyphosphate, glassy Sodium carbonate Sodium chlorite Sodium fluoride Sodium hydroxide Sodium metabisulfite Sodium polyphosphate, glassy Sodium silicate Sodium silicofluoride Sodium tripolyphosphate Sodium zinc polyphosphate, glassy Sodium zinc potassium polyphosphate, glassy Sulfur dioxide Sulfuric acid Tetrasodium pyrophosphate

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5 stances, including information on possible genotoxic effects. Next, a suggested no-adverse-response level (SNARL) 2 was calculated for a potential contaminant. Irrespective of known aenotoxic itv . a SNARL mav be calculated f rem existing data such as threshold limit value (TLV), which is available from a number of sources, and other para- meters, including average body weight, intake, and expo- sure. In most cases, the calculated SNARL value differed from the TLV or the maximum contaminant level (MCL) found in the National Interim Drinking Water Regulations (NIDWR).3 In general, the committee felt it would be appropriate to utilize the MCL in calculating the allowable contami- nant level contributed by an impurity in a water treatment chemical, unless there was no current MCL for that impur- ity or where there was new information concerning either the toxicity of the contaminant or the current status of the MCL. In the case of lead, recent toxicological data are available that led the committee to recommend to the EPA that a lower MCL should be considered. However, the committee did not feel it consistent to adopt a smaller number in its calculations at this time. A SNARL or MCL was thus converted to a recommended maximum impurity content (RMIC) in the additive by the following equation: RMIC = = SNARL or MCL MD x SF SNARL or MCL (mg/liter) x 106 mg/kg l- MD (mg/liter) x SF Maximum dosage (MD) for the water treatment chemical was based upon maximum patterns known by the committee to be representative of water treatment practice. The safety factor (SF) used in the calculation of the RMIC was 10, reflecting the view of the committee that no more than 10% of a given SNARL or MCL value should be contributed by a given impurity in a water treatment chemical. Some may argue for a higher safety factor, but 10 was chosen by the committee as reasonable in view of other uncertainties and approximations relating to the fate of impurities introduced during treatment. A sample calculation of a RMIC is as follows:

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6 Contaminant (Hg): Water Treatment Additive MCL 0.002 mg/liter : Maximum Dose (MD) Safety Factor 500 mg/liter 10 RMIC = 0~002 me Hg/liter x 1o6 mg/kg 500 mg Additive/liter x 10 RMIC = 0.4 mg Hg/kg Additive Table 2 contains RMIC values for impurities of concern at selected additive dose levels reported to one significant figure. RMIC values are also contained in the individual monographs and should be compared to impurity concentra- tions obtained by using the sample preparation described in the monograph. m at is, the RMIC values represent maximum recommended impurity content and as such can be used as guidelines to the industry. The user is advised that, if actual dosages applied exceed those upon which the monograph is based, appropriate RMIC value should be extrapolated from Table 2. The committee is aware that for some direct additives analyses of generally available grades show the presence of impurities at levels well below those that would be calculated as a RMIC. In such cases, RMIC values are not calculated, and the purity requirements are derived from those analyses. If cases are found in which a contaminant may create additional health concern because of its radioactivity, RMIC values shall be calculated in accordance with radia- tion limits that appear in the Code of Federal Regula- tions.~ The RMIC levels are based upon information available to the committee. It is obviously impossible to recommend maximum impurities content levels for all possible unusual or unexpected impurities, the presence of which would de- pend upon method of manufacture and quality of raw mater- ial used. If other than recognized methods of manufacture or if unusual raw materials are used, the user should re- quire appropriate certification of purity from the vendor or manufacturer to demonstrate the water treatment chemi- cal is suitable for its application in the preparation of potable water. Material regenerated or reclaimed at the plant site or point of use must also meet Codex specifi- cations.

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7 Genotoxic Effects The genotoxic potential of water treat- ment chemicals impurities was evaluated on a case by case basis. Appropriate data bases were investigated and pup fished risk assessments considered. Epigenetic Effects Evidence for epigenetic effects was considered where appropriate. However, as in the case of carbon tetrachloride, sufficient data were not available to use epigenetic mechanisms as sole basis for determining minimum contaminant levels. Analytical Methods Preferred sampling, sample prepara- tion, and analytical methods for the determination of impurities are cited. It is recognized that a number of water treatment chemicals require special sample prepar- ation and/or analysis due to matrix or other effects. For such chemicals the recommended special procedures are included in the Codex. Methods that are cited or appear in the Codex should be considered the preferred analytical procedures; alter- native methods may be used if they can be shown to be equivalent. Revision It is expected that the Codex will be reviewed continuously and annual supplements issued. The supple- ments may contain additional chemicals and revisions of the monographs contained in the present Codex, as well as revision of analytical procedures. LITERATURE CITED 1. Code of Federal Regulations, 40:141, 1981. 2. Safe Drinking Water Committee. 1980. Drinking Water and Health. National Academy of Sciences, Washington, D.C. 70 pp. 3. Environmental Protection Agency. 1976. National Drinking Water Regulations. EPA-570/9-76-003. Environmental Protection Agency, Washington, D.C. 4. American Water Works Association. 1981. Standard for Ammonium Sulfate. AWWA B302-81. American Water Works Association, Denver, Colorado.

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