radioactivity and the who guidelines for drinking-water ... · radioactivity but natural uranium is...

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Radioactivity and the WHO

Guidelines for Drinking-water

Quality

John Fawell

Member of GDWQ Expert Committee


Published

2011


The Guidelines

Provides scientific point of departure for developing

drinking-water standards around the world.

Large number of countries see The Guidelines as the

first port of call for advice on drinking-water quality.

In a chemical or microbiological emergency they are

also an early source of information in the absence of

more detailed advice.

Radioactivity is normally of minor concern compared to

microbiology and some chemical contaminants.


Radiological Aspects

Introduced in the first edition of the Guidelines published in 1984.

Introduced screening values

0.1 Bq/litre for gross alpha activity

1.0 Bq/litre for gross beta activity

Assumes 2 litres water consumed per day for an adult for one year.

Values considered to be sufficiently precautionary.

Vast majority of supplies easily meet the screening values.


Subsequent Editions

Based on recommended reference level of committed effective dose of

0.1 mSv from 1 year’s consumption.

Represents < 5% of the average effective dose attributable annually to

natural background radiation.

Provides information on how to interpret an exceedence of the

reference level of dose for common radionuclides.

Screening value for gross alpha increased to 0.5 Bq/litre in the third

edition

Guidelines do not apply in emergency situations – but how do they

apply in a post-emergency situation


Chapter 9 of the WHO DWQG takes into

account the latest ICRP recommendations


Sources of Drinking Water

There are three main sources of water used for deriving

drinking water.

These are:

Groundwater, often well protected from surface

contamination but not always.

Rivers, vulnerable to many sources of

contamination. Wastewater discharges.

Reservoirs and lakes, often river fed.


Drinking-Water Varies

Drinking-water can be delivered by large municipal

supplies, often with significant resources, particularly in

developed countries.

There are also many small rural individual or community

supplies that are often poorly resourced and very basic.

This means that the capability to monitor or screen for

contaminants, particularly radioactivity is variable but for

radioactivity it usually varies from limited to none.

The same applies to treatment options except many large

supplies in developed countries have advanced treatment.


Drinking-Water Production

Groundwater may be very limited treatment, particularly if

from a well-protected, stable source.

Surface water will usually receive greater levels of

treatment, particularly for larger municipal supplies,

following the multi-barrier approach to ensuring drinking-

water safety. Can include coagulation and sedimentation,

and filtration that in modern systems in developing

countries will include membranes.

Small supplies receive much more limited treatment but

increasingly point of use devices available.


Radiation Issues for Drinking-Water

Radon and radon daughters. Primarily a groundwater issue.

Uranium. Also groundwater. Chemical toxicity and possibly

radioactivity but natural uranium is less of an issue for radioactivity in

spite of public perception. Some areas suffer badly from contamination

from uranium mining that can impact surface waters.

Man-made discharges to surface water. Usually extremely low levels,

e.g. Hospitals, laboratories, nuclear establishments.

Post-emergency contamination? What form? Fortunately experience is

limited.


Radon

Dealt with in more detail in the fourth edition.

Readily lost from water to atmosphere - showering, dish

washers, washing machines, boiling all are good at

releasing radon to atmosphere. Issue is inhalation not

ingestion.

Problem often in small supplies with limited resources.

Not an emergency issue but does it need to be considered

in determining overall exposure for some regions in a post

emergency scenario?


Uranium

Guideline value based on chemical toxicity.

Original guideline value of 15 µg/litre based on laboratory

animal data but increased to 30 µg/litre in the fourth edition

based on more recent human data. May be very

conservative but still uncertainties, therefore provisional.

To detect radioactivity by gross screening need >100 µg/l

so 30 µg/litre is also protective of radioactivity.

Again the difficulty is small, resource limited supplies.

Likely to need consideration post emergency?


Complications Following Emergencies

Treatment works sludge. Coagulation and sedimentation good at removing

radionuclides (not tritium) but can mean high levels in sludge so disposal

needs to be considered. Also filtration media. E.g.Chernobyl – radionuclides

deposited by rain in NW UK removed from surface water efficiently into sludge

normally disposed of to land remained an issue post-emergency.

Communities reliant on rainwater may be vulnerable for a short period but

unlikely to be an issue post-emergency. They will not be measuring

radioactivity – advice needed.

Must not undermine confidence in the available water supply, particularly

where limited or no alternatives.

Need to be sure there are alternative supplies or actions that can be taken if

significant post emergency contamination. Alternative supplies can be a

significant logistical problem, particularly for cities and long periods.


Water is Used in Cooking and Irrigation

Latter probably less of a problem post emergencies

unless extended period of exposure to contaminated

water.

The former needs to be considered if higher guidance

values for drinking water are to be put in place and there

is likely to be other significant exposure from food.

Cooking rice and pasta, for example, results in take up

of water and some contaminants.


15

Different Guidance for Similar Sources

+

+

Reference dose 0.1 mSv/annum

for an adult for drinking-water.

Reference dose 5.0 mSv/annum

from all food


Perception and Trust

There is usually little choice in drinking-water.

Providing alternative sources can be logistically very

difficult and affects subsequent actions.

If a decision to issue a ‘Do Not Drink’ order then need to

have clear basis for withdrawal of the order.

Mixed or unclear messages lead to mistrust.

Drinking-water is very sensitive in the public perception.

Make sure any measurements are correct.


GDWQ questions and challenges

Important to know where to measure , e.g. at source, post treatment,

both

Evaluate if children should be considered in HBT and subsequent

guideline values as risks can be higher.

Clear guidance on interpretation of screening measurements for

compliance

Effectiveness of household treatment and other treatment at community

or regional level (experience in Japan post Fukushima)

Limitations of screening techniques for some nuclides?


Use of WHO guidelines

Confusion over use of different guidance levels/action

levels in event of an accident/incident

– Further clear explanation needed in DWQ guidelines

• When do emergency and ‘normal’ criteria/guideline values apply?


Questions

– Can technology (treatment) be used to provide assurance that

levels of radioactivity are controlled and therefore minimise

monitoring needed?

• Turbidity being used in Japan as secondary indicator of Cs levels in DW

– Very little capacity in many countries for analysis - need simple

basic methods.


Finally

Need to have clear description of where emergency

values come from, how they relate to ‘normal’ values

and how they should be used, taking into account

differing circumstances and time-frames.

Co-ordination of international values and ensuring that

the reasons for any differences are clearly described.

Most of the people who need guidance have little

technical background but they need to have confidence

in the advice given.

Consistency is a key requirement.

radioactivity and the who guidelines for drinking-water ... · radioactivity but natural uranium is...

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