Jack Cornett

Mercury in arctic air: the long-term trend.

The long-term (1974-2000) time trend of total filterable mercury (TFM) in the air in the Canadian Arctic is reported. The concentration of TFM had declined by (3.0+/-0.8) % and (3.1+/-0.9) % per year in the summer and fall, respectively, over the 27 years, which coincided with the calculated reduction rate of world-wide mercury emission (~3.3% per year) from human activities between 1983 and 1995. The time trend for winter and early spring was not statistically significant as the variability of TFM was very large, partly due to Arctic Mercury Depletion Events and partly due to Arctic haze.

Preventing uranium hydride formation in standard uranium samples for determination of 239Pu by ICP-MS

UH+ interference poses considerable difficulties for the determination of 239Pu in samples with high uranium content. A new approach for reducing this interference was developed. Substitution of water with heavy water (D2O) as a solvent in uranium standard solution eliminated the major source of UH+ ions and reduced the UH+/U+ ratio from a typical value of 1.33 × 10−5 to a very low value of 2.60 × 10−7. The method allows the determination of low levels of 239Pu in samples containing 106 fold excess of uranium. The detection limit for 239Pu in a sample containing 10 ppm of uranium was determined as 0.58 ± 0.03 ppt. A kinetic isotope effect of ca. 1.4 was observed for the reaction of U+ with hydrogen (H) compared with the reaction with deuterium (D). The magnitude of this effect is in agreement with the value calculated based on the collision theory.

Polonium-210: lessons learned from the contamination of individual Canadians

This paper describes the radioactive poisoning episode in London in 2006 and the Health Canada response to locate and test any Canadians who might have been contaminated by this event. The search strategies and testing methods are explained and the results given. The lessons learned are summarised and implications for vulnerable populations are discussed. The greatest public health impact was probably the generation of fear and concern, especially among those prone to health-related anxiety disorders. The groups of individuals at risk were effectively managed by a single point of contact system combined with rapid triage and counselling that was provided to everyone to address their individual concerns.

Method intercomparison for the analysis of 239/240Pu in human urine

Following a radiological or nuclear emergency, medical intervention requires rapid assessment of the exposure of people usually through determination of internal dose. For the plutonium urine bioassay, besides thermal ionization mass spectrometry (TIMS) and alpha spectrometry methods, inductively coupled plasma mass spectrometry (ICP-MS) methods have been recently developed, which can provide much higher sample throughput. In this work, three ICP-MS methods were compared with one TIMS method and two alpha spectrometry methods for the measurement of 239Pu and 240Pu in human urine samples spiked at different concentration levels. The sample throughputs for all three ICP-MS methods are similar: each instrument measures about 80 samples in the first 24 hours and 200 samples in the first 48 hours following the emergency event, if the samples arrive at the laboratory 8 hours after the event occurs. Method accuracy and precision were determined using ANSI N13.30. Method detection limits and minimum detectable amounts (MDA) were determined to evaluate method sensitivities. The sensitivities of the three ICP-MS methods were also compared with the derived urine action level (24 h urine, 500 mSv committed effective dose equivalent, inhalation exposure, maximum dose conversion factor) to evaluate their applicability to exposure situations.

Measurement of 236U in human tissue samples using solid phase extraction coupled to ICP-MS

236U is present at ultra-trace levels in typical environmental and biological samples. Typically, it has been measured by highly sensitive techniques, such as accelerator mass spectrometry. This paper reports the measurement of 236U in 20 human tissue samples using a sector field ICP-MS following automated SPE separation. The tissue samples were selected from one USTUR case, representing tissues/organs that are important for internal radiation assessment. Another uranium isotope, 235U, was also measured in the samples. The results for 235U were compared with those obtained by alpha spectrometry. For most cases, results from the two methods were comparable, indicating that the measurement of 236U in the samples is reliable.

Achievements and current activities of the Canadian radon program.

Based on new scientific information and broad public consultation, the Government of Canada updated the guideline for exposure to indoor radon and launched a multi-year radon program in 2007. Major achievements accomplished in the past 3 y and current activities underway are highlighted here.

Fast methods for 239Pu faecal bioassay

For timely monitoring of internally contaminated individuals following radiological or nuclear emergency events, two fast bioassay methods were developed for the measurement of 239Pu in faecal samples, one for a sample representing 24-hour excretion and the other for a sample representing 10% of 24-hour excretion. Samples were decomposed either by ashing/microwave digestion or by acid refluxing. They were measured by ICP-MS following solid phase extraction using TEVA resin from Eichrom®. The two methods were assessed against performance criteria for radionuclide bioassay defined by ANSI N13.30 for their accuracy and repeatability. Both methods satisfy the requirements and are sensitive enough for emergency population screening. The method for small samples has a much shorter sample turnaround time, making its application more promising.

Recent Transport History of Fukushima Radioactivity in the Northeast Pacific Ocean

The large inventory of radioactivity released during the March, 2011 Fukushima Dai-ichi nuclear reactor accident in Japan spread rapidly across the North Pacific Ocean and was first observed at the westernmost station on Line P, an oceanographic sampling line extending 1500 km westward of British Columbia (BC), Canada in June 2012. Here, time series measurements of 134Cs and 137Cs in seawater on Line P and on the CLIVAR-P16N 152°W line reveal the recent transport history of the Fukushima radioactivity tracer plume through the northeast Pacific Ocean. During 2013 and 2014 the Fukushima plume spread onto the Canadian continental shelf and by 2015 and early 2016 it reached 137Cs values of 6-8 Bq/m3 in surface water along Line P. Ocean circulation model simulations that are consistent with the time series measurements of Fukushima 137Cs indicate that the 2015-2016 results represent maximum tracer levels on Line P and that they will begin to decline in 2017-2018. The current elevated Fukushima 137Cs levels in seawater in the eastern North Pacific are equivalent to fallout background levels of 137Cs that prevailed during the 1970s and do not represent a radiological threat to human health or the environment.

Considerations and preliminary design of patient exposure registry.

To aid in protecting patients from unnecessary exposures and to reduce radiation burdens to the public, a system for tracking a patients medical exposure history and related radiation doses would be a useful tool. A patient-centred exposure registry, the Patient Exposure Registry (PER), is a mechanism that provides this tracking. This article outlines the objectives of the proposed Canadian PER together with considerations and preliminary design of the registry. Implementation strategy is discussed. The strategy will allow many initiatives progressing in parallel such as backward data mining and forward development in order to make this important registry a reality in the near future.

Increased zinc concentrations in the Canadian Arctic air

Abstract Long–term time trends for heavy metals in Canadian arctic surface air were studied recently. Different from the continuing decrease for other metals, such as cadmium and mercury, from 1973 to 2000, zinc concentrations decreased from 1973 to the mid–1980s and then increased again at Resolute (74.7°N, 95.0°W). Its concentrations in the surface air increased from less than 10 ng m -3 in the mid–1980s winters to more than 20 ng m -3 in the late 1990s winters. A sharper increasing trend was found at another arctic site, Coral Harbour (64.2° N, 83.3° W), where Zn increased from about 10 ng m -3 in air in the early 1970s to more than 100 ng m -3 in late 1990s. The increase was also recognized at two sub–arctic sites, Churchill (58.8° N, 94.1° W) and Moosonee (51.3° N, 80.6° W), but not in more southerly sites like Ottawa (45.3° N, 75.7° W) and Windsor (42.3° N, 83.0° W). The possible reasons which led to the Zn increase in the north are discussed in this paper.