Radioactivity in Ottawa Drinking Water

Background

The City’s drinking water continues to meet or be better than all federal guidelines and provincial standards for radiological parameters including tritium.

In recent months there has been increased media attention on the subject of radioactivity in the Ottawa River and potential effects on Ottawa’s drinking water supply. Much of the focus has been on radioactive “leaks” from the Chalk River nuclear reactor and the public reporting of these events by the Canadian Nuclear Safety Commission. The City of Ottawa has received a number of public inquiries about the safety of our drinking water supply. This memo will provide an update on the City monitoring program and test results over the last eight years. It is important to note that the drinking water supply remains safe and well within the standards for radioactive substances in drinking water established by Health Canada.

Sources of Radioactive Substances

Radionuclides are found in the environment both as naturally occurring elements and as products and byproducts of various nuclear technologies (e.g. medical isotopes, nuclear power). By far the greatest contribution to the average public radiation exposure comes from naturally occuring radioactive elements in the Earth's crust, and from radionuclides that originate in deep space. In fact, these natural sources contribute more than 98% of the average human radiation dose, not including individual medical exposures¹.

Radionuclides in Drinking Water

Typically, the contribution to total radiation exposure from drinking water is small and is largely due to naturally occurring radionuclides. However, the presence of nuclear power facilities or other nuclear industries within the watershed area means that there is the potential for release of artificial radionuclides as well.

The artificial radionuclides of greatest concern from a health perspective in terms of the potential for normal or accidental release from nuclear fuel industries into drinking water supplies are tritium, strontium-90, iodine-131, caesium-137 and radium-226. Average tritium concentrations in surface waters across Canada are on the order of 5 to 10 Bq/L (Becquerels per Litre), owing primarily to residual fallout from atmospheric weapons testing during the 1950’s and 1960’s.

In the case of the Ottawa River, there is potential for tritium releases resulting from operations at the Chalk River nuclear facility located upstream near Deep River, Ontario. Tritium (3H) is a contaminant that cannot be removed through the drinking water treatment process. For these reasons, the City of Ottawa conducts extensive monitoring of river and treated water samples to ensure the safety of the drinking water supply.

Drinking Water Guidelines for Radionuclides

Health Canada (1995) has established safe drinking water guidelines for 14 natural and 64 artificial radionuclides, expressed as maximum acceptable concentrations in Bq/L. However, rather than test for all 78 radionuclides, drinking water quality is assessed through several “screening” tests that measure the aggregated radiation from alpha and beta particles. If the “screening” level is below the lowest radionuclide limit, then drinking water safety is inferred. If an exceedance is observed, then detailed analysis is carried out to determine the specific element present and to verify that the drinking water supply is safe for human consumption.

A revised guideline for radiological parameters is currently in preparation by Health Canada, and is expected to be posted over the next several months. In addition, the Ontario Drinking Water Advisory Council to the Ministry of Environment has reviewed the guideline for tritium in drinking water and is expected to post additional recommendations for monitoring and responding to tritium levels in drinking water. City staff will be reviewing these updated documents as they become available.

International Limits for Tritium in Drinking Water

The guidelines for radionuclides in drinking water adopted by the majority of the international community are based on international radiation protection methodologies and recommendations of the International Commission on Radiological Protection (ICRP) and the World Health Organization (WHO) ².

The following is a table summarizing the limits for tritium in drinking water³:

Country / Organization	Tritium Limit for Drinking Water (Bq/L)
Canada (Ontario)	7,000
European Union	100⁴
Finland	30,000
Australia	76,103
Russia	7,700
Switzerland	10,000
United States	740
WHO	10,000

The City of Ottawa test results for tritium in drinking water average from 5 to 6 Bq/L. As seen from the above table, the City’s drinking water is well below current limits for tritium. There are on-going discussions within the regulatory community to revise and likely lower the current limit for tritium in drinking water.

It is important to note that the tritium concentration in the City of Ottawa’s drinking water is very low and we expect to meet future standards.

Ottawa’s Monitoring Program

For Ottawa’s drinking water supply, three radioactive parameters are monitored weekly, namely gross alpha, gross beta and tritium. Weekly test results give an adequate trend of river water quality since changes occur on a gradual basis over many weeks owing to the size and flowrate of the Ottawa River. It is worth noting that there are separate monitoring programs for each of the Lemieux Island and Britannia Water Purification Plants. The combined test results from the two sites give a more detailed picture of Ottawa River water quality.

As a matter of explanation, the gross alpha and gross beta tests are “screening level” tests that include all 78 potential radioactive parameters based on whether they emit alpha or beta particles as they decay. These screening levels have been set as the lowest level Maximum Acceptable Concentration (MAC) for all radionuclide parameters. Should the screening level be exceeded more detailed analyses are carried out to identify the specific individual radionuclide(s) that are causing the radioactivity.

Summary of Results 2000 - 2008

For the City of Ottawa's ongoing monitoring program, please refer to the table below, which summarizes the results observed from 2000 to 2008 for the three test parameters.

Over many years of monitoring, the results in the table demonstrate that the gross alpha and gross beta results have been safely within the prescribed screening levels. For this reason, it has not been necessary to carry out detailed analyses for the individual radionuclides.

For tritium, the measured levels are typically in the 5 to 6 Bq/L range. This level of tritium is comparable to background concentrations in most Canadian lakes and rivers. It is also well below the safe drinking water standard of 7000 Bq/L, established by Health Canada.

It is on the basis of these figures that we are able to state that the City's drinking water meets or is better than all radiological standards.

The ongoing weekly monitoring program for gross alpha, gross beta, and tritium will continue for both water treatment plants. Test results will continue to be reported publicly through annual Summary Reports to City Council with analytical summaries, including radiological results. In addition, City staff are working with the Canadian Nuclear Safety Commission to improve communication protocols and response procedures in the event of a spill.

For more information, please contact the City of Ottawa by telephone by calling 3-1-1 (TTY: 580-2401) or by email at Info-Water@ottawa.ca

Summary of Radioactivity Results for City of Ottawa Raw and Treated Water

2000 - 2008
Lab Analysis by Radiation Protection Bureau (Health Canada) & DWSP Lab (Ontario Ministry of Environment)
YEAR		gross-Alpha (Bq/L)		gross-Beta (Bq/L)		Tritium (Bq/L)
YEAR		Britannia	Lemieux	Britannia	Lemieux	Britannia	Lemieux
2000	Ave.	< 0.04	< 0.04	0.04	0.04	< 5.0	< 5.0
	Range	(<0.04 - <0.04)	(<0.04 - <0.04)	(<0.01 - 0.08)	(0.01 - 0.09)	(<5.0 - <5.0)	(<5.0 - <5.0)
	# of Tests	N = 4	N = 2	N = 57	N = 53	N = 4	N = 2
2001	Ave.	< 0.04	< 0.04	0.04	0.04	< 5.0	< 5.0
	Range	(<0.04 - <0.04)	(<0.04 - <0.04)	(<0.01 - 0.08)	(0.02 - 0.08)	(<5.0 - <5.0)	(<5.0 - <5.0)
	# of Tests	N = 4	N = 4	N = 56	N = 56	N = 4	N = 4
2002	Ave.	< 0.04	< 0.04	0.04	0.05	< 5.0	< 5.0
	Range	(<0.04 - <0.04)	(<0.04 - <0.04)	(0.01 - 0.10)	(0.02 - 0.13)	(<5.0 - <5.0)	(<5.0 - <5.0)
	# of Tests	N = 2	N = 2	N = 54	N = 54	N = 2	N = 2
2003	Ave.	< 0.04	< 0.04	0.05	0.04	< 5.0	5.3
	Range	(<0.04 - <0.04)	(<0.04 - <0.04)	(0.02 - 0.12)	(0.01 - 0.09)	(<5.0 - <5.0)	(5.0 - 6.0)
	# of Tests	N = 2	N = 4	N = 44	N = 46	N = 2	N = 4
2004	Ave.	< 0.04	< 0.04	0.05	0.04	< 5.0	< 5.0
	Range	(<0.04 - <0.04)	(<0.04 - <0.04)	(<0.01 - 0.20)	(<0.01 - 0.07)	(<5.0 - <5.0)	(<5.0 - <5.0)
	# of Tests	N = 2	N = 2	N = 53	N = 53	N = 2	N = 2
2005	Ave.		< 0.04	0.04	0.04		5.4
	Range	N/A	(<0.04 - <0.04)	(0.01 - 0.09)	(0.01 - 0.07)	N/A	( 5.1 - 5.6)
	# of Tests		N = 2	N = 51	N = 51		N = 2
2006	Ave.	< 0.04	< 0.04	0.04	0.04	5.4	5.9
	Range	(<0.04 - <0.04)	(<0.04 - <0.04)	(0.02 - 0.06)	(0.02 - 0.07)	(<5.0 - 8.4)	(5.9 - 14.0)
	# of Tests	N = 2	N = 2	N = 9	N = 10	N = 5	N = 5
2007	Ave.	0.01	0.02	0.04	0.04	< 5.0	< 5.0
	Range	(<0.01 - 0.02)	(<0.01 -< 0.03)	(<0.01 - 0.07)	(<0.01 - 0.09)	(<5.0 - 21.3)	(<5.0 - 29.9)
	# of Tests	N = 8	N = 9	N = 49	N = 47	N = 51	N = 52
2008	Ave.	0.01	0.01	0.05	0.04	5.2	5.0
	Range	( <0.01 - 0.03)	( <0.01 - 0.03)	(<0.01 - 0.11)	(0.01 - 0.08)	(<5.0 - 22.8)	(<5.0 - 11.5)
	# of Tests	N=45	N=52	N=45	N=52	n=45	n=54
		gross-Alpha (Bq/L)		gross-Beta (Bq/L)		Tritium (Bq/L)
Drinking water guidelines*		0.10(Bq/L)		1.0(Bq/L)		7000(Bq/L)

*Guidelines for Canadian Drinking Water Quality – Health Canada
< means less than analytical detection limit
N/A – no data available

¹ Guidelines for Canadian Drinking Water Quality (Health Canada) – Radiological Characteristics:² Standards and Guidelines for Tritium in Drinking Water, January 2008, Canadian Nuclear Safety Commission³Current as of September 2007⁴ The EU does not use this number as a limit but rather a screening value to indicate the possible presence of other artificial radionuclides

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