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Revised Fact Sheets on Chloral Hydrate and Monochloramine submission

ID: 
5
This submission reflects the views of
Organisation Name: 
Department of Health (WA)
Please identify the best term to describe the Organisation: 
Government department – State / Territory
Personal Details
Questions for Public Consultation
1. Is the information that is presented in the fact sheet relevant and easy to understand?: 

 

Comments:

Yes.

2. Do you have any comments on the proposed increase in the proportion of total daily intake of chloral hydrate that will be attributable to water (changing from 20% to 80%)?: 

Comments:

No comments.

 

3. Do you have any comment on the use of the two-year rodent study to derive the guideline value for chloral hydrate, rather than the 90-day study used for the current guideline value? Are you aware of other studies that should be considered? : 

Comments:

No comments and not aware of other studies.

4. Do you have any other comments on the proposed change to the guideline value for chloral hydrate, from 0.02 mg/L to 0.1 mg/L? : 

Comments:

The covering sheet about the consultation process, this submissions form, and the body of the fact sheet itself, describe this chemical by its common name (“chloral hydrate”), whereas the main header for the fact sheet, the alphabetical list of guideline values in Table 10.5 and the index of fact sheets on page xxii of ADWG all list it as “Trichloroacetaldehyde (chloral hydrate)” i.e. it is listed alphabetically under “T”.  The proposed fact sheet text never refers to the chemical as “trichloroacetaldehyde”.

It would be preferable if the finalised fact sheet for chloral hydrate was easy to locate when inserted into ADWG.  It is recommended that you settle on the common name “chloral hydrate” as the preferred nomenclature, use that term consistently throughout, and list it alphabetically accordingly.

The term “trichloroacetaldehyde” should be inserted parenthetically after “chloral hydrate” in the heading of the fact sheet (i.e reversing the current order of the terms), and after the first use of that term in the fact sheet.

An entry “Trichloroacetaldehyde (see chloral hydrate)” should also be inserted under “T” in the various indexes and Table 10.5 as a cross-reference.

5. Is the information that is presented in the fact sheet relevant and easy to understand?: 

Comments:

Under the heading “Health Considerations” in the draft monochloramine fact sheet, a sentence states:

“Acute haemolytic anaemia has been reported in haemodialysis patients when tap water containing chloramines was used for dialysis.”

The source of information for this statement should be cited in the References section.  If the purpose of the statement is to remind water suppliers that tap water containing chloramines should not be used for dialysis, then it is strongly recommended that the fact sheet state this in more direct terms, as that is a key health-related matter that water suppliers need to be mindful of.

It is recommended to add a caveat along the lines of:

Water suppliers are reminded that tap water containing chloramines should not be used for dialysis.  Water suppliers that disinfect with chloramines should contact their jurisdiction’s health agency to seek advice on how to communicate with home dialysis patients or dialysis clinics in this regard”.

This will better tie this fact sheet in with section 3.8.2 of the 12 element framework (p.47) and maintain consistency with the Information Sheet on page 1132 of ADWG, which states in part:

“Chloramines present in water are harmful to people on kidney dialysis and to animal species in aquaria; therefore, it is important for water utilities using chloramination to inform consumers at risk.”

6. Do you have any comments on the rounding process that has been used in the calculation to derive the guideline value for monochloramine?: 

Comments:

A rounding process used in the Monochloramine computations appears to be disclosed in the covering information about the derivation of the guideline value, but not in the fact sheet itself.  There appear to be two rounding steps involved and they round in opposite directions (i.e. 3.3 is rounded down to 3 but 4.5 is rounded up to 5).

It is unusual to find health-related guidelines at a level that can impinge on operational considerations in running a water supply, but that is the case here, with the proposed monochloramine guideline value of 3 mg/L adversely affecting the capacity of a chloraminated system to maintain adequate disinfecting capability over long lengths of pipeline.

The problem with allowing 5 mg/L, expressed as chlorine, as an alternative way of measuring monochloramine levels, is that it amounts to a rounding upwards of over 20% (20.9%) of the true converted value of 4.1 mg/L.  It is simply not credible to anyone who does the calculations to say that 5 mg/L, expressed as chlorine, is equivalent to 3 mg/L of monochloramine.

This difficulty appears to be caused by a desire to keep guideline values to one significant figure.  While this is usually a laudable aim, there are a number of exceptions to be found in the ADWG (the figure of 0.017 mg/L for uranium comes to mind), and this is a case in point, where two significant figures are required to walk the tightrope between health-based considerations and operational requirements, without straining credulity as to the numbers.

If we use two significant figures, the numbers in the two equations come to 3.3 mg/L for monochloramine, and 4.5 mg/L, when expressed as chlorine.  The latter figure is rounded down by a minor amount (of 1.1%) from the true converted value of 4.55 mg/L, but still gives the operators of chloraminated systems the flexibility they need to run them safely from a disinfection point of view.

It is therefore recommended that the result of the two equations in the “Derivation of Guideline” section of the fact sheet be expressed to two significant figures (i.e. 3.3 mg/L instead of 3 mg/L and 4.5 mg/L instead of 5 mg/L), and that the health-related guideline statement be shown accordingly as:

Based on health considerations, the concentration of monochloramine in drinking water should not exceed 3.3 mg/L (equivalent to 4.5 mg Cl as Cl2/L).

It would also be acceptable to delete any reference in the head line statement to equivalency when expressed as chlorine (i.e delete the section “equivalent to N mg Cl as Cl2/L”).  Detail about equivalency to chlorine for the purposes of being measured by the “standard DPD ferrous titrimetric methods” can be explained fully in the “Derivation of Guideline” section of the fact sheet, where N = 4.5, without needing to be inserted in the head line.

7. Do you have any other comments on the proposed change to the guideline value for monochloramine, from 3 mg/L (equivalent to 4.1 mg Cl as Cl2/L) to 3 mg/L (equivalent to 5 mg Cl as Cl2/L)?: 

Comments:

Whatever the final decision on this matter, a consequential amendment will be required to the chlorine fact sheet.  Based on the above recommendation, the health-related guideline for chlorine should be shown as:

Based on health considerations, the guideline value for total chlorine in drinking water is 5 mg/L, except for chloraminated systems, where a guideline value of 4.5 mg/L applies.  [Instead of 4.1 mg/L, as shown currently.]

Page reviewed: 19 December, 2014