A Guideline for Evaluating Drinking Water in terms of Naturally Occurring Radioactivity

10. Describing water quality in terms of its radioactivity content

The quality of water is described in terms of five water quality classes, each uniquely characterized by a colour. These water quality classes represent ranges of annual dose for daily use of a specific water source, associated health effects and typical exposure scenarios. Table 10.1 on the next page describes the different ranges of water quality.

The dose calculation method described in Appendix 1 estimate the annual dose for various age groups as well as the lifetime average annual dose. The following approach is followed for determining water quality:

2. If the difference between the minimum and maximum of these doses is less than a factor of five, calculate the weighted life-time average dose and use it for classification purposes.

3. If the difference between the minimum and maximum of these doses is more than a factor of five, use the maximum age specific dose for initial classification purposes.

No dose calculation method is presented for the rare event that artificial nuclides are detected in a water resource. In these cases special collaboration is required between DWAF, the NNR and the management of the practice that is the origin of these nuclides.

11. Water analysis and calculating the annual dose, D

11.1. Introduction

The extent of nuclide analysis of water should be a function of the following factors:

These factors serve as basis for defining three categories of water sources that are defined and discussed in the section that follows.

11.2. Methods for determining annual dose estimates

11.2.1.Introduction

The assumed initial conditions for a water resource that requires evaluation are as follows:

Table 10.1: Different Ranges of Water Quality

*Class /Colour*	*Dose range; mSv/a*	*Health Effects and Typical Exposure Scenarios*	*Intervention Decision* *Time Frames*
Class 0 (Blue - Ideal water quality)	0.01 – 0.10	· There are no observable health effects. · This is the range of exposure from ideal quality water sources. · Most treated water falls in this water quality range. · Additional doses that result from human activities that fall within this range are difficult or impossible to determine and/or to distinguish from variations in background doses with sufficient confidence.	Intervention not applicable for this class of water.
Class 1 (Green - Good water quality)	> 0.10 – 1	· There are no observable health effects. · It is the range of exposure from some natural and untreated water sources (e.g. ground water / wells) as well as water sources that could be influenced by mining and mineral processing activities. · A dose between 0.2 to 0.8 mSv/a is the typical worldwide range of ingestion radiation dose resulting from water as well as food. · A dose equal to 1 mSv/a corresponds to the regulatory public dose limit for human activities involving radioactive material.	No intervention is required although ALARA principles apply.
Class 2 (Yellow - Marginal water quality)	> 1 – 10	· A small increase in fatal cancer risk associated with this dose range. · Probably only a small number of natural water sources of this quality exist, resulting from exceptional geological conditions. · Abnormal operating conditions at some nuclear certified mineral and mining processes may result in a dose in this range when a person drinks the untreated water. Intervention will most likely be required to improve the quality of water that is released into the public domain. · The total natural background radiation from all exposure pathways, not only water, falls in this range.	Intervention considerations within 2 years.
Class 3 (Red - Poor water quality)	> 10 – 100	· Health effects are statistically detectable in very large population groups. · This range represents excessive exposure. · It is highly unlikely to find water of this poor quality in the natural environment.	Intervention is required in less than 1 year.
Class 4 (Purple - Unacceptable water quality)	> 100	· Health effects may be clinically detectable and a significant increase in the fatal cancer risk (greater than one in a thousand). · A dose greater than 100 mSv can usually only occur during a major accident at a nuclear facility. These facilities have to demonstrate that such an accident cannot happen with a frequency of more than once in a million years.	Immediate intervention is required.

There is normallyno statistical dose correlation for uranium chemical concentration and gross alpha concentration, as is the case for the Klip river and Mooi river studies. It can be deduced from these studies that each water body or catchment area will have its own unique correlation between dose and uranium chemical concentration. This relation can only be established after many samples over a period of time. It was also shown that gross alpha activity concentrations could not be accurately correlated with dose.

The method for assessing water quality must avoid giving overly conservative results that could create wrong initial perceptions regarding the water quality. These perceptions are usually difficult to change afterwards. However, it is still required to have the precautionary principle included in the water quality assessment method so that the probability is low for underestimating dose in situations of elevated NORM concentrations.

Two different methods, as well as a combination of the two methods, are used, to determine the annual dose, D, (described in section 11.2.2 and 11.2.3) for the following three categories of water:

· Category A water use:

It is untreated water from a natural source (e.g. directly from a borehole, canal, river/stream or dam) with a low probability of being influenced by a mining and mineral processing activity.

· Category B water use:

It is untreated water from any source with a significant probability of being influenced by a mining and mineral processing activity e.g. a surface stream or borehole inside the potential impact radius of a mining and mineral processing facility.

· Category C water use:

It is treated water from a formal water source (e.g. water service providers such as Rand Water Board or a municipal waterworks) providing drinking water to a large number of people.

11.2.2.Calculation Method 1: A screening method

The screening method is designed to optimise costs without compromising the precautionary principle, when water may result in a high dose.

A two-nuclide measurement vector is required to perform an initial screening dose assessment, i.e. U-238 and Ra-226. Gross alpha specific activity and uranium chemical concentration do not allow a dose assessment of the required accuracy in the beginning. However, these two parameters are also measured and are used to check the validity of analysing only for U-238 and Ra-226. Low-probability nuclide behaviour, for example, a high relative abundance of Th isotopes, should be indicated by a low U concentration (ug/L) and a high gross alpha-activity concentration. This would then indicate a requirement for a detailed radioanalysis.

The dose is estimated using a six-nuclide calculation vector consisting of the following nuclides and assumptions:

U-234 in equilibrium with U-238

Pb-210 and Po-210 in equilibrium with Ra-226

U-235 = U238 ¸ 21.7

Note: U-235 was included since it has a fairly constant natural abundance in relation to U-238. Some laboratories provide U-235 along with U-238 and the measured value can then be used.

The screening method, which is intended for category A water, has relatively poor accuracy at very low radioactivity concentrations (dose in the range 0.01 mSv/a to 0.10 mSv/a) when compared to a calculation using a nuclide vector consisting of all measurable nuclides in the U-238, U235 and Th-232 decay chains. However, the assumption of Pb-210 and Po-210 in equilibrium with Ra-226, introduces adequate conservatism to flag a situation when the overall radioactivity concentration in the water increases and a typical constraint dose value 0.30 mSv/a is approached. At higher radioactivity concentrations the dose has a high probability of not being underestimated because of the conservative assumption regarding Po-210 and Pb-210.

The age group specific and lifetime average annual dose associated with a water resource is calculated as described in Appendix 1.

11.2.3.Method 2: A detailed method

Water sources used by a large number of people would require a larger nuclide measurement vector initially; due to collective dose considerations. As soon as acceptable correlation can be demonstrated between Method 2 and the Method 1 screening dose assessment, say after a year’s monitoring, Method 1 can be used on a routine basis.

Method 2 is similar to Method 1 except that larger measurement and calculation vectors are used, as indicated in Table 11.1. Nuclides that are measured appear in bold letters. Unmeasured short-lived progeny are assumed to be in equilibrium with their parent nuclide except for the following nuclides:

Ra-228 is assumed to be in equilibrium with Th-232.
Ac-227 and Pa-231 are assumed to be in equilibrium with U-235.

Table 11.1 Method 2 Nuclide Calculation Vector

Nuclide
U-238
Th-234
Pa-234m
*U-234*
*Th-230*
*Ra-226*
*Pb-210*
Bi-210
*Po-210*
Th-232
Ra-228
Ac-228
*Th-228*
*Ra-224*
*U-235*
Th-231
Pa-231
Ac-227
Th-227
Ra-223

11.2.4.Comments on monitoring frequency and water analysis methods

Samples should be taken so that they are representative of the quality of the water consumed throughout the year.

The initial monitoring frequency should be quarterly, except where extraordinary nuclide concentrations exist (e.g. D > mSv/a) and more frequent monitoring is justified.

Sampling should preferably coincide with the monitoring programmes for other water contaminants. A comparative risk assessment of the pollutants in a water resource is essential in order to set priorities for water treatment. Radioactivity is only one of many agents that can cause adverse health effects, and in many cases in South Africa, it is secondary to some biological pollutants occurring in water that is used by informal settlements.

11.2.5.Framework for nuclide analysis and decision making

A framework for radioanalyses and water annual dose calculation is presented in Table 11.2.

Table 11.2 Analysis and Decision Making Guide

Category of water source

Initial Analysis Method /

Analyses

Nuclides in dose calculation and equilibrium assumptions

Annual Dose, D

Further actions

Routine Monitoring /

Comments

Untreated water from a natural source not influenced by mining and mineral processing

Method 1 – Screening method

· U-238

· Ra-226

· Gross alpha specific activity

· U chemical concentration

· U-238 – U-234

· Ra-226 – Pb-210 – Po-210

· U-235 = U-238 ¸ 21.7

D < 1 mSv/a

· No further action required except to inform water users.

· Whenever gross alpha > (2´ U-238 + 3´ Ra-226) then recommend a Method 2 analysis to determine the dose more accurately.

· Annual monitoring

D > 1 mSv/a

· Perform water evaluation using Method 2

· If D £ 1 mSv/a following Method 2 analysis then no further action except to re-inform users and perform routine confirmatory monitoring.

· If D > 1 mSv/a when using Method 2, intervention considerations are required.

· 3- monthly monitoring

Untreated water from an informal source potentially influenced by mining and mineral processing

Method 1 – Screening method

· U-238

· Ra-226

· Gross alpha specific activity

· U chemical concentration

· U-238 – U-234

· Ra-226 – Pb-210 – Po-210

· U-235 = U-238 ¸ 21.7

D < 0.3 mSv/a

· No further action if total exposure from all exposure pathways to the critical group D £ 0.30 mSv/a; if not, perform Method 2 analysis to determine the dose accurately.

· 3- monthly monitoring

· Liaison between NNR and DWAF required. Consult the impact assessment of the authorised activity.

0.3 mSv/a < D < 1 mSv/a

· Re-assess dose by using Method 2.

· No further action if total exposure to the critical group D £ 1 mSv/a and an optimised constraint cannot be achieved at less than 1 mSv/a

D > 1 mSv/a

· Confirm dose by using Method 2.

· Intervention options to be evaluated (if mining and mineral processing is responsible for elevated radioactivity levels then definite remedial actions required)

· 3- monthly monitoring.

· Liaison between DWAF and NNR required.

Treated water delivered by a formal water distribution network (towns/cities)

Method 2:

· U-238, Ra-226, Th-230, Pb-210, Po-210, Th-232, Ra-228, Th-228, Ra-224, Ra-223, Pa-231, Ac-227

· Gross alpha specific activity;

· U chemical concentration

U-238 – Th-234 – Pa-234m – U234

U-235 = U-238 ¸ 21.7

D £ 0.1 mSv/a

· No further action

· 3 - monthly monitoring during first year.

· For routine monitoring after first year use Method 1.

· There is a high probability that the water source will meet recommended dose value of D = 0.10 when it is subjected to typical water treatment processes.

· WHO guideline: provisional level of 2 ug/l uranium in drinking water.

D > 01 mSv/a

· No further action if D £ 1 mSv/a and cost effective lowering of the dose cannot be achieved; if D > 1 mSv/a then special investigations required to lower dose to £ 1 mSv/a.

14. References

[1] Institute for Water Quality Studies Reports:

(1) Report on the Radioactivity Monitoring Programme in the Klip River Catchment -Institute for Water Quality Studies: Department of Water and Sanitation. August 2000

(2) Report on the Radioactivity Monitoring Programme in the Mooi River (Wonderfonteinspruit) Catchment Institute for Water Quality Studies: Department of Water and Sanitation. May 1999

[2] IAEA Fact Sheet - Radiation in everyday life

[3] Hall, E. J. 1976. Radiation and Life

[4] Gonzalez, A.J. Decision-Making about Chronic Radiation Exposure to the Public: New Recommendations from the ICRP (The paper is an executive summary of an ICRP report titled: Protection of the Public in Situations of prolonged Exposure – The Application of the Commission’s System of Radiological Protection to Controllable Exposure due to Natural Sources and Long Lived Radioactive Residues)

[5] World Health Organization Guidelines for Drinking Water Quality, Geneva. 1993

[6] Ivanovich, M. 1982. Uranium Series Disequilibrium: Applications to Environmental Problems

[7] International Commission on Radiological Protection (ICRP). 1990 Recommendations of the ICRP on Radiological Protection. ICRP Publication 60

[8] The Royal Society of Chemistry 1996. Environmental Impact of Chemicals: Assessment and Control

[9] Health Physics Society (1996). Radiation Risk in Perspective: position statement of the Health Physics Society

[10] EPA United States Environmental Protection Agency – Office of Water: Current Drinking Water Standards

[11] Official Journal of the European Communities: Council Directive 98/83/EC

[12] Report EUR 19255 May 2000. European Commission – Nuclear Safety and the Environment; Radiological Impact due to Wastes containing Nuclides from Use and Treatment of Water

[13] Commission Recommendation of 8 June 2000 on the application of Article 36 of the Euratom Treaty concerning the monitoring of the levels of radioactivity in the environment for the purpose of assessing the exposure of the population as a whole (2000/473/Euratom)]

[14] Sources and effects of ionising Radiation United Nations Scientific Committee on the Effects of Atomic Radiation; UNSCEAR 2000 Report to the General Assembly

[15] Akiba, S. Cancer Risks in the High Background Radiation Areas in Yangjiang, China, and in Kaunagappaly, India. IRPA 2000

[16] US EPA federal Guidance Report No.13 September 1999. Cancer Risk Coefficients for Environmental Exposure to Radionuclides

[17] Winde, Frank. Slimes dams as source of uranium contamination of streams – the Koekemoer Spruit (Klerksdorp Gold-field) as a case study. COM of SA Conference on Environmentally Responsible Mining, South Africa, Muldersdrift, Johannesburg, 25-28 September 2001

[18] International Atomic Energy Agency, Vienna 1996. International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources. Safety Series 115

Institute for Water Quality Studies

Department of Water and Sanitation