radioactivity and the who guidelines for drinking-water ... · radioactivity but natural uranium is...
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TITLE from VIEW and SLIDE MASTER | September 10, 2014 1 |
Radioactivity and the WHO
Guidelines for Drinking-water
Quality
John Fawell
Member of GDWQ Expert Committee
TITLE from VIEW and SLIDE MASTER | September 10, 2014 2 |
Published
2011
TITLE from VIEW and SLIDE MASTER | September 10, 2014 3 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 4 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 5 |
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
TITLE from VIEW and SLIDE MASTER | September 10, 2014 6 |
Chapter 9 of the WHO DWQG takes into
account the latest ICRP recommendations
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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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 8 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 9 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 10 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 11 |
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?
TITLE from VIEW and SLIDE MASTER | September 10, 2014 12 |
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?
TITLE from VIEW and SLIDE MASTER | September 10, 2014 13 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 14 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 15 |
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
TITLE from VIEW and SLIDE MASTER | September 10, 2014 16 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 17 |
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?
TITLE from VIEW and SLIDE MASTER | September 10, 2014 18 |
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?
TITLE from VIEW and SLIDE MASTER | September 10, 2014 19 |
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.
TITLE from VIEW and SLIDE MASTER | September 10, 2014 20 |
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.