Tag Archives: epidemiology

Is there a cancer threat from the Oil Sands industry?

by Peggy Olive

Those of us who watched “Tipping Point: The Age of the Oil Sands” on The Nature of Things at the end of January [1] are legitimately concerned by this question.  The Kelly and Schindler publication in the prestigious scientific journal PNAS [2] provided evidence that mining the Athabasca Oil Sands has increased the levels of carcinogens in the environment downstream of the industry, and it follows that more carcinogens in the environment could mean a higher risk of developing cancer for the exposed population.

Demonstrating that the Oil Sands have caused an increase in cancer incidence is another matter.  This is largely because cancer is so prevalent; one in three of us can expect to develop cancer over a lifetime and one in five may die from it.  According to the 2010 Canadian Cancer Statistics [3], the incidence rates for all cancers have not changed much across Canada in thirty years, and the current incidence of cancer in Alberta is somewhat lower than that in the Atlantic Provinces.  Rates of incidence for all cancers between 2004-2006 in the Northern Lights Regional Authority, which includes the small town of Fort Chippewyan downstream of the Oil Sands development, are lower or equal to the Alberta provincial average [4].  However, in 2009, The Alberta Health Services presented a comprehensive study of cancer incidence in the Fort Chipewyan residents between 1995 and 2006, concluding that there was an increase in cancer incidence (51 cases observed with 39 expected in about 1200 individuals); this included two cases of a very rare form of bile duct cancer [5].  With so few total cases, caution was correctly placed on the interpretation of this observation and whether the increase could be attributed to the Oil Sands chemicals alone.  Nonetheless, continued monitoring of this population was advised because of the unexpected cancer incidence.

What we really need are answers to more difficult questions: Can the current cancer risk be considered “acceptable”, as suggested by the 2010 Royal Society report on the Oil Sands [6], are all reasonable efforts being made to mitigate the risk, and will prompt regulatory action be taken when the risk is no longer considered acceptable (if it currently is)? These are not simple questions to answer because first we need to know:

  1. The chemical nature of the toxins from the tar sands industry (there are potentially dozens, each with its own distribution within the environment).  Unfortunately, it is not possible to know pre-industry levels of these chemicals, and the adequacy and credibility of results obtained by the industry-supported regional aquatic monitoring program (RAMP) have come under serious question [7].
  2. Which chemicals have been tested and classified as human carcinogens.   Ideally, any interactions between different chemicals that may affect cancer risk should also be known.
  3. The doses of carcinogens delivered to the population (including information on the concentration, duration of exposure, and route of exposure).   Ideally, biomonitoring of individuals (for example, in hair or urine) should also be performed where warranted by higher levels in the environment.
  4. Regulations concerning exposure limits for each carcinogen, and whether these limits have been approached or exceeded downstream of the Oil Sands industry
  5. The number of individuals exposed to the carcinogens in order to estimate the number of excess cancer cases that can be expected, and the significance one can place on this estimate
  6. What has been done, and what can be done, to mitigate the risks of developing cancer

Taking the position that no increase in cancer risk is acceptable fails to acknowledge the many risks to our health that we accept each day, including risks of developing cancer from lifestyle choices.  The government sets limits on the levels of known carcinogens in the environment, but these limits are often meant to be “as low as reasonably achievable” and therefore are typically greater than zero.  For ionizing radiation, perhaps the best understood carcinogen (and my own area of expertise), the current dose limit is 1 mSv per year for the general public.  Yet a single medical imaging procedure can deliver ten times that dose, and the natural background dose (which is highly variable from one place to another) averages three times higher [8,9].  To put these amounts into perspective, exposure to 1 mSv would be expected to produce five extra cancer deaths in 100,000 people [9].   It would be impossible to demonstrate a statistically-significant increase in cancer incidence by exposure of small numbers of  individuals to 1 or even 10 mSv per year, yet we are still able to estimate the probability for a large population provided we know the exposure.

It often comes back to risk versus benefit.  We all find it easier to accept risk when it is our choice to make, but First Nations and others who make their homes downstream of the Oil Sands may not have that option.  Both risks and benefits need to be shared fairly, and that is not often the case.

Dozens of toxic chemicals are emitted and distributed during the mining and processing of the Oil Sands.  Arsenic is a known human carcinogen, yet a 2006 report prepared by Cantox Environmental for Alberta Health and Wellness concluded that there was a negligible risk of cancer from exposure to inorganic arsenic in the Woods Buffalo region of Alberta that contains the Oil Sands [11].  Although the levels of arsenic used for those cancer risk estimates were provided by the Oil Sands industry, in independently-funded studies, arsenic levels were rising in that area but did not exceed the regulatory limit [2,12].  However, seven of twelve other toxic metals exceeded guidelines for the protection of aquatic life by 5 -300 fold [2].  Heavy metals, including cadmium and mercury, are considered ‘possible’ human carcinogens, a different designation that limits what can be said about the risk for developing cancer.

Polycyclic aromatic hydrocarbons (PAHs) include known human carcinogens that are found downstream of the Oil Sands.  Twenty-six out of twenty-eight measured PAHs showed, on average, a six fold increase in concentration downstream compared to upstream [13].  Canada Health and Welfare and the World Health Organization recommend drinking water levels for total PAHs of 0.2 mg/L, and for the most carcinogenic PAH, benzo(a)pyrene, the limit is set at 0.01 mg/L.  The estimated lifetime risk associated with the ingestion of drinking water containing 0.01 µg/L benzo[a]pyrene is considered “essentially negligible” by Health Canada, and 1 in 100,000 by the World Health Organization [14].   In a study conducted in 2007 by Timoney [15], concentrations of PAHs near the Oil Sands varied greatly, but at times exceed guidelines suggesting potential danger to exposed individuals.  Perhaps we should be asking, “How dangerous is the exposure to PAHs from the tar sands industry relative to smoking cigarettes or living in an urban environment?  How rapidly are levels increasing downstream of the Oil Sands?  What are the peak levels as well as average levels?”  Answering these questions requires a reliable environmental monitoring program which is currently lacking.

Simply demonstrating that the amount of any one carcinogen is lower than government mandated limits fails to acknowledge the possible interactions between different chemicals.   Co-exposure of fish to arsenic and benzo(a)pyrene can increase rates of genotoxicity eight to eighteen times above rates observed after exposure to either carcinogen alone [16].  Currently, there is little if any information on additive or multiplicative risks of cancer from exposure to several carcinogens, so the possibility is largely ignored in assigning ‘safe’ limits.

With known carcinogens being distributed over a large region of Alberta, reducing exposure and subsequent risk should be an industry priority.  In the 1970s, stack precipitators were instrumental in reducing airborne particulates, but subsequent industry expansion means that overall levels are now similar to those measured before precipitators were installed [2].  Levels will continue to rise in coming years if no efforts are made to further reduce emissions.  Tailings ponds should not leak as they do now [13], and they should be guarded against storm damage.  River water flow should be monitored so that it is adequate to dilute particulates, and climate change effects and usage effects on river flow should be taken into consideration for future expansion.  Technology should be developed to recover toxic heavy metals.

What is needed to make this happen is a world-class, government-sponsored environmental monitoring system that can keep pace with the oil sands developments, is transparent but informative to the public, and examines a full range of potential environmental effects.  Water testing should be as good if not better than the air quality measurements now provided by the Woods Buffalo Environmental Association, a multi-stakeholder group that publishes readouts on their web site from more than a dozen sites in the Oil Sands region [17].  Information on levels of carcinogens present in plants, animals and people living in the region are also needed.

A special review panel recently convened by the Alberta Government has already concluded that more stringent oversight of environmental contamination in the Athabasca Oil Sands is necessary [18].  Their full report is due in June 2011, but recognizing that the current monitoring program is flawed and doing something about it are two separate things.  Maximum toxic contaminant levels need to be set, and not just for water, but also for soil, sediment, plant and animal life.  There should be recognition that adhering to these levels may mean curtailing expansion at some future point.  The pressure to accomplish these goals must come from many directions, and should not rest exclusively on the inhabitants of Northern Alberta.

Coming back to the question, is there a cancer threat from the Oil Sands, the answer is yes, because the levels of known carcinogens in the regions downstream of the industry have increased.  Have these increases actually caused cancer?  Perhaps, but the available data do not support an unequivocal conclusion.  Cancer is too prevalent, and the number of exposed individuals is too small to be sure.  Does this mean that there is no reason for concern, at least at present?  Absolutely not.  Cancer can take many years to develop and levels of carcinogens from the industry continue to increase.  Until a reliable monitoring system is in place, we will have insufficient information to base estimates of cancer risk.

The Oil Sands industry has the opportunity and the responsibility to mitigate these risks, but we have a responsibility to understand these risks in relation to others we encounter in our daily lives.  Hall, in an earlier edition of his book [9] examined the chances of dying from a radiation-induced cancer in relation to the risk of dying from smoking cigarettes or driving a given number of highway miles.  I’ve used his analogy to compare PAH-induced cancer with these risks.  If drinking water containing 0.01 mg/L benzo(a)pyrene causes one additional fatal cancer in 100,000 people, this would be equivalent to the risk of dying from smoking 73 cigarettes or driving 178 miles.  This doesn’t sound too bad until we remember that we are also exposed to many carcinogens not only in drinking water but in the air we breathe and the food we eat.  One of those chemicals is arsenic.  The risk of dying from cancer by drinking water containing 0.01 mg/L arsenic (the government mandated limit) is equivalent to the risk of dying by smoking 1500 cigarettes or driving 3500 miles.  If you’re wondering why maximum allowable arsenic levels are so high, it’s partly because of the difficulties in estimating both exposure and risk from cancer caused by arsenic.  However, Health Canada also states that their regulation represents “the lowest level of arsenic in drinking water that can be technically achieved at reasonable cost” [19], which is even more reason for close monitoring of the carcinogens produced by the Oil Sands industry.


1.     Tipping Point: The Age of the Oil Sands.  Documentary film aired Jan 27 and Feb 12, 2011 on CBC-TV. http://www.cbc.ca/documentaries/natureofthings/2011/tippingpoint/

  1. Kelly, EN, Schindler, DW, Hodson PV, Short JW, Radmanovich, R. Oil Sands development contributes elements toxic at low concentrations to the Athabasca River and its tributaries.  Proceedings of the National Academy of Sciences, 107: 16178–16183 2010.
  2. Canadian Cancer Society’s Steering Committee: Canadian Cancer Statistics 2010, Toronto: Canadian Cancer Society, 2010. http://www.cancer.ca/canada-wide/about%20cancer/cancer%20statistics/~/media/CCS/Canada%20wide/Files%20List/English%20files%20heading/pdf%20not%20in%20publications%20section/Canadian20Cancer20Statistics2020102020English.ashx
  3. Alberta Health Services, Report on Cancer Statistics in Alberta, 2009. http://www.albertahealthservices.ca/poph/hi-poph-surv-cancer-cancer-in-alberta-2009.pdf
  4. Alberta Cancer Board, Report on the Incidence of Cancer in Fort Chipewyan, 1995-2006 http://www.albertahealthservices.ca/rls/ne-rls-2009-02-06-fort-chipewyan-study.pdf
  5. Royal Society of Canada Expert Panel, Environmental and Health Impacts of Canada’s Oil Sands Industry, December, 2010. http://www.rsc.ca/documents/expert/RSC%20report%20complete%20secured%209Mb.pdf
  6. Main, C.  2010 Regional Aquatics Monitoring Program Scientific Review http://www.ramp-alberta.org/UserFiles/File/RAMP%202010%20Scientific%20Peer%20Review%20Report.pdf
  7. The 2007 Recommendations of the International Commission on Radiological Protection.  ICRP #103;  Wrixon, AD. New ICRP recommendations.  Journal of Radiological Protection, 28:161-168, 2008. http://iopscience.iop.org/0952-4746/28/2/R02/pdf/jrp8_2_R02.pdf
  8. Hall EJ and Giaccia, AJ, Radiobiology for the Radiologist, Sixth Edition, Lippincott Williams & Wilkins, Philadelphia, 2006.

10.  Smith AH, Lopipero PA, Bates MN, Steinmaus CM.  Arsenic epidemiology and drinking water standards.  Science 296: 214l5-6, 2002;  Kaiser J. Second Look at Arsenic Finds Higher Risk, Science 293, 2189, 2001; Arsenic in drinking water. National Academy Press, 2001 Update. http://www.nap.edu/openbook.php?record_id=10194&page=203

11.  Report prepared by Cantox Environmental for Alberta Health and Wellness.  Assessment of the Potential Lifetime Cancer Risks Associated with Exposure to Inorganic Arsenic among Indigenous People living in the Wood Buffalo Region of Alberta, 2007.

12.  Timoney, KP and Lee P.  Does the Alberta Tar Sands industry polute?  The Scientific evidence.  The Open Conservation Biology Journal 3:65-81, 2009.

13.  Kelly EN, Short JW, Schindler, DW, Hodson PV, Ma M, Kwan AK,  and Fortin, BL.  Oil sands development contributes polycyclic aromatic compounds to the Athabasca River and its tributaries.  PNAS 106:22346-22351, 2009.

14.  Ministry of Environment, Lands and Parks, Province of British Columbia. Ambient water quality criteria for polycyclic aromatic hydrocarbons (PAHs) http://www.env.gov.bc.ca/wat/wq/BCguidelines/pahs/index.html#TopOfPage

15.  Timoney, KP. A study of water and sediment quality as related to public heath issues, Fort Chipewyan, Alberta.  A report conducted on behalf of the Nunee Heath Board Society, Fort Chipewyan, Alberta. http://energy.probeinternational.org/system/files/timoney-fortchipwater-111107.pdf

16.  Maier A, Schumann BL, Chang X, Talaska G, Puga A. Arsenic co-exposure potentiates benzo(a)pyrene genotoxicity. Mutation Research, 517: 101-11, 2002.

17.  Wood Buffalo Environmental Association Website: http://wbea.org/component/option,com_frontpage/Itemid,1/

18.  Jones, J.  (Reuters) Water checks deficient at Canada Oil Sands: Report, March 10, 2011 http://solveclimate.com/news/20110310/water-checks-deficient-canada-oil-sands-report

19.  Health Canada Environmental and Workplace Health, Arsenic, Application of the Guideline. http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/arsenic/application-eng.php

Climate change indicators

by Stan Hirst

The evidence of human influences on climate change has become increas­ingly clear and compelling over the last several decades There is now convincing evidence that human activities such as electricity pro­duction and transportation are adding to the concen­trations of greenhouse gases that are already naturally present in the atmosphere. These heat-trapping gases are now at record-high levels in the atmosphere com­pared with the recent and distant past.

The U.S. Environmental Protection Agency has recently published Climate Change Indicators in the United States to help the concerned public readers interpret a set of important indicators  for climate change. The report presents 24 indicators, each describing trends in some way related to the causes and effects of climate change. The indicators focus primarily on the United States, but in some cases global trends are presented in order to provide context or a basis for comparison.  The following is a brief summary of the report’s contents.

Greenhouse Gases

Global Greenhouse Gas Emissions. Worldwide, emissions of greenhouse gases from human activities increased by 26 percent from 1990 to 2005. Emissions of carbon dioxide, which account for nearly three-fourths of the total, increased by 31 percent over this period. The majority of the world’s emissions are associated with energy use.

Atmospheric Concentrations of Greenhouse Gases. Concentrations of carbon dioxide and other greenhouse gases in the atmosphere have risen substantially since the beginning of the industrial era. Almost all of this increase is attributable to human activities. Histori­cal measurements show that the current levels of many greenhouse gases are higher than any seen in thousands of years, even after accounting for natural fluctuations.

Climate Forcing. From 1990 to 2008, the radiative forcing of all the greenhouse gases in the Earth’s atmosphere increased by about 26 percent. The rise in carbon dioxide concentrations accounts for approximately 80 percent of this increase. Radiative forcing is a way to measure how substances such as greenhouse gases affect the amount of energy that is absorbed by the atmosphere – an increase in radiative forcing leads to warming while a decrease in forcing produces cool­ing.

Weather and Climate

U.S. and Global Temperature. Average temperatures have risen across the lower 48 states since 1901, with an increased rate of warming over the past 30 years. Parts of the North, the West, and Alaska have seen temperatures increase the most. Seven of the top 10 warmest years on record for the lower 48 states have occurred since 1990, and the last 10 five-year periods have been the warmest five-year periods on record. Average global temperatures show a similar trend, and 2000–2009 was the warmest decade on record worldwide.

Heat Waves. The frequency of heat waves in the United States decreased in the 1960s and 1970s, but has risen steadily since then. The percentage of the United States experi­encing heat waves has also increased. The most severe heat waves in U.S. history remain those that occurred during the “Dust Bowl” in the 1930s, although average temperatures have increased since then.

Drought. Over the period from 2001 through 2009, roughly 30 to 60 percent of the U.S. land area experienced drought conditions at any given time. However, the data for this indicator have not been collected for long enough to determine whether droughts are increasing or decreasing over time.

U.S. and Global Precipitation. Average precipitation has increased in the United States and worldwide. Since 1901, precipitation has increased at an average rate of more than 6 percent per century in the lower 48 states and nearly 2 percent per century worldwide. However, shifting weather patterns have caused certain areas, such as Hawaii and parts of the Southwest, to experience less precipitation than they used to.

Heavy Precipitation. In recent years, a higher percentage of precipitation in the United States has come in the form of intense single-day events. Eight of the top 10 years for extreme one-day precipitation events have occurred since 1990. The occurrence of ab­normally high annual precipitation totals has also increased.

Tropical Cyclone Intensity. The intensity of tropical storms in the Atlantic Ocean, Caribbean, and Gulf of Mexico did not exhibit a strong long-term trend for much of the 20th century, but has risen noticeably over the past 20 years. Six of the 10 most active hurricane seasons have occurred since the mid-1990s. This increase is closely related to variations in sea surface temperature in the tropical Atlantic.


Ocean Heat. Several studies have shown that the amount of heat stored in the ocean has increased substantially since the 1950s. Ocean heat content not only determines sea surface temperature, but it also affects sea level and currents.

Sea Surface Temperature. The surface temperature of the world’s oceans increased over the 20th century. Even with some year-to-year variation, the overall increase is statisti­cally significant, and sea surface temperatures have been higher during the past three decades than at any other time since large-scale measurement began in the late 1800s.

Sea Level. When averaged over all the world’s oceans, sea level has increased at a rate of roughly six-tenths of an inch per decade since 1870. The rate of increase has accelerated in recent years to more than an inch per decade. Changes in sea level relative to the height of the land vary widely because the land itself moves. Along the U.S. coastline, sea level has risen the most relative to the land along the Mid-Atlantic coast and parts of the Gulf Coast. Sea level has decreased relative to the land in parts of Alaska and the Northwest.

Ocean Acidity. The ocean has become more acidic over the past 20 years, and studies suggest that the ocean is substantially more acidic now than it was a few centuries ago. Rising acidity is associated with increased levels of carbon dioxide dissolved in the water. Changes in acidity can affect sensitive organisms such as corals.

Snow & Ice

Arctic Sea Ice. Part of the Arctic Ocean stays frozen year-round. The area covered by ice is typically smallest in September, after the summer melting season. September 2007 had the least ice of any year on record, followed by 2008 and 2009. The extent of Arctic sea ice in 2009 was 24 percent below the 1979 to 2000 historical average.

Glaciers. Glaciers in the United States and around the world have generally shrunk since the 1960s, and the rate at which glaciers are melting appears to have accelerated over the last decade. Overall, glaciers worldwide have lost more than 2,000 cubic miles of water since 1960, which has contributed to the observed rise in sea level.

Lake Ice. Lakes in the northern United States generally appear to be freezing later and thawing earlier than they did in the 1800s and early 1900s. The length of time that lakes stay frozen has decreased at an average rate of one to two days per decade.

Snow Cover. The portion of North America covered by snow has generally decreased since 1972, although there has been much year-to-year variability. Snow covered an average of 3.18 million square miles of North America during the years 2000 to 2008, compared with 3.43 million square miles during the 1970s.

Snowpack. Between 1950 and 2000, the depth of snow on the ground in early spring decreased at most measurement sites in the western United States and Canada. Spring snowpack declined by more than 75 percent in some areas, but increased in a few others.

Society & Ecosystems

Heat-Related Deaths. Over the past three decades, more than 6,000 deaths across the United States were caused by heat-related illness such as heat stroke. However, consider­able year-to-year variability makes it difficult to determine long-term trends.

Length of Growing Season. The average length of the growing season in the lower 48 states has increased by about two weeks since the beginning of the 20th century. A particularly large and steady increase has occurred over the last 30 years. The observed changes reflect earlier spring warming as well as later arrival of fall frosts. The length of the growing season has increased more rapidly in the West than in the East.

Plant Hardiness Zones. Winter low temperatures are a major factor in determining which plants can survive in a particular area. Plant hardiness zones have shifted noticeably northward since 1990, reflecting higher winter temperatures in most parts of the country. Large portions of several states have warmed by at least one hardiness zone.

Leaf and Bloom Dates. The timing of natural events such as leaf growth and flower blooms are influenced by climate change. Observations of lilacs and honeysuck­les in the lower 48 states indicate that leaf growth is now occurring a few days earlier than it did in the early 1900s. Lilacs and honeysuckles are also blooming slightly earlier than in the past, but it is difficult to determine whether this change is statistically meaningful.

Bird Wintering Ranges. Some birds shift their range or alter their migration habits to adapt to changes in temperature or other environmental conditions. Long-term stud­ies have found that bird species in North America have shifted their wintering grounds northward by an average of 35 miles since 1966, with a few species shifting by several hundred miles. On average, bird species have also moved their wintering grounds farther from the coast, consistent with rising inland temperatures.