In this instance, I do not believe that this clarification improves water quality or public health outcomes, and may in its application undermine public confidence in water supplies.
In this instance, I very strongly believe that this should not be incorporated into the ADWG. There are a number of reasons for this. For example, consider an arsenic sample, analysed on new generation instrumentation with a measured concentration of 0.0149 ± 0.0001 mg/L. This would be interpreted as not exceeding the guideline. As many current regulations require providers to report an incident if they are aware of a result that exceeds guidelines; a provider who did not report this value would be compliant.
Note: if the analytical value was 0.015 ± 0.005 mg/L, this is to be considered as an exceedance (despite it being less accurate than the previous result). Values close to the guideline (however interpreted) will always pose this problem at the boundary. However, all that occurs if this change in the interpretation is implemented is that the effective guideline - the reporting requirement which is viewed by providers as pass/fail - will increase in some cases by up to 50%. Can we justify such a change?
1) Laboratory testing and reporting.
A laboratory determines the limit of detection and limit of reporting of their analytical method. The analytical results are then reported to the level of accuracy of the analytical method, not to the number of significant figures in the guideline value to which the value is to be compared.
The analytical value determined may well be accurately and precisely known to be numerically higher than the published ADWG health guideline value (as in the As example above), and the certificate of analysis may state that the value is greater than the ADWG health guideline (e.g. especially where the analytical value is known to a high precision).
2) Water Managers
On receipt of a precise analytical value that is numerically greater than the ADWG Health Guideline, it is simple for a water manager (who may or may not have formal analytical chemistry or public health training, e.g .may be a plumber or engineer) to compare the analytical value on the certificate of analysis to the numerical value of the guideline. A direct comparison (ie pass/ fail interpretation) does not require an understanding of sampling error, analytical uncertainty, the specific derivation of the relevant guideline value (whether the guideline relates to acute or chronic effects), or other information provided in the factsheet. The number is either less than or equal to the guideline, or above. If the ADWG recommends immediate reporting to the relevant regulator when a value is above the guideline, public health should be appropriately managed in all cases.
3) Regulatory reporting
In most jurisdictions at present, the current requirement is that the result above the ADWG health guideline is reported to the relevant regulator. This is as regulation should be: clear, easy to understand, easy to educate, easy to regulate, easy to implement. Most importantly, it is both easy to understand and transparent to the general public. The ADWG should support the current system, and not conflict with it. Retaining the status quo also ensures that drinking water data interpretation is consistent with other reporting requirements (e.g. Environmental Authorities typically treat chemical water quality as Pass/Fail against ANZECC guidelines, or stated discharge limits).
When a provider reports the result, this will initiate a process whereby trained Public Health Professionals review and interpret the data, and can then provide appropriate advice as to the appropriate management response as required.
If this change is made, regulation across Australia will need to be clarified to ensure that providers reporting responsibilities are clear. This will inevitably introduce conflicts between the ADWG and the legally enforceable legislation/regulation. Conflicts between regulation and the ADWG will undermine the application of the framework.
4) Public Health Professionals
The public health regulators, on becoming aware of the numerical value greater than the health guideline, are the appropriate professionals that should then make a judgement call as to the public health impact (if any) of the value. This advice is therefore appropriate to be given to those professionals, but not the wider industry. By quickly referring an incident, or potential incident, Public health professional can evaluate the available evidence that led to the derivation of the guideline, and consider the specific circumstances of the provider and the value. If the public health advice is that due to the significant figures in the guideline value that no action is necessary, this is appropriate. But is it the case that they should not be made aware at all which is what this change would result in?
Confusing the application of the ADWG:
What is the public perception? Joe and Joan Public, with no scientific training, may nonetheless be interested to read their water suppliers annual report. In that report, the provider will indicate that they measured Arsenic, with a maximum value of 0.0149 mg/L. The annual report will also indicate that they had no drinking water incidents. Given that the ADWG states the health guideline value for Arsenic is 0.01 mg/L it will appear to them that their provider detected a parameter at nearly 1.5 times the health guideline value, and took no action.
It is also interesting to note that the As value has already been rounded up from the 2004 version where it was 0.007 mg/L. If this change is accepted, a provider who detects As at 0.014 mg/L in 2016 will not have to report an exceedence (ie the new effective guideline is more than double the previous guideline.)
Interestingly, there is a water treatment plant in Queensland that has recently been upgraded to remove Arsenic that by this reasoning was potentially not above the guideline value (interpreted as proposed). Was that upgrade even required?
Is it not better from all angles that an exceedance was reported to the health authorities, and that all recommended actions (if any) were undertaken?
Summary:
This change appears to be solving a problem by creating a bigger one.
It is not clear that this interpretation is consistent with the precautionary approach recommended by the 6th guiding principle.
Alternate suggestion: "Any chemical result that exceeds the relevant ADWG Health Guideline value at the level of precision reported by the analysing laboratory should be immediately reported to the relevant health authority."
This could be clarified by developing a more detailed fact sheet
“Public Health implications for values close to the Health Guideline Value – information for public health professionals”.
This document can then provide more detail for health regulators as to which evidence to weigh, and recommendations for actions. The provision of this type of advice will still allow competent providers to discuss the appropriate response to a value that is slightly above the guideline value with health professionals, but will not confuse the less technically proficient providers.
