Air quality regulations and programs are vital for protecting the public from harms caused by air pollution. To support these actions, numerous epidemiological studies have sought to identify the pollutants most responsible for adverse outcomes. These studies often used statistical adjustments for copollutants in outcome regression models, a practice also commonly applied to assess interactions between copollutants. Here, we highlight possible pitfalls of multipollutant analyses. Indiscriminate copollutant adjustment can induce noncausal associations through collider adjustment, distorting effect estimates for individual air pollutants. We describe the underlying mechanisms and provide empirical evidence on how such bias may realistically influence the relationships between air pollution and health outcomes from a well-characterized Canadian national cohort alongside a simulation study. Additionally, we discuss strategies to mitigate the impact of this bias. Given the widespread interest in multipollutant approaches among the scientific and policy communities, greater caution is needed when conducting and interpreting research on multiple pollutants.

OBJECTIVE:Differential reason-for-testing may bias test-negative estimates. This study aimed to estimate healthcare worker SARS-CoV-2 risk, with adjustment for healthcare-seeking behavior and unmeasured reason-for-testing. METHODS:A total of 1.2-million workers in Ontario, Canada, were followed for SARS-CoV-2 polymerase chain reaction tests from February 2020 to December 2021. Hazard ratios (HRs) were used to estimate SARS-CoV-2 risk in healthcare workers versus non-healthcare workers based on the overall and test-negative subcohort. Unmeasured reason-for-testing was examined through probabilistic bias analyses. RESULTS:In the test-negative subcohort, healthcare and non-healthcare workers had a similar risk of SARS-CoV-2. However, healthcare workers had an increased risk in the symptomatic-adjusted (HR: 1.15, 95% confidence interval: 1.03-1.40) and asymptomatic-adjusted (HR: 2.83, 95% confidence interval: 1.08-9.07) models. CONCLUSIONS:Future test-negative studies should account for potential bias from varying symptomatic and asymptomatic testing groups and may consider using probabilistic bias analysis methods when reason-for-testing data is missing.

BACKGROUND:During the 2023 wildfire season, Ontario, Canada, had unprecedented wildfire smoke, but the health impact on the population is unknown. We aimed to quantify the acute impact of the wildfire smoke on respiratory and cardiovascular outcomes across Ontario. METHODS:We conducted a quasi-experimental study by leveraging the timing of 2 consecutive wildfire smoke episodes in June 2023. Heavy wildfire smoke blanketed much of Ontario on 2 occasions, in early June and again in late June, causing severely degraded daily air quality. Following the epidemiologic triangulation framework, we collected health data on emergency department visits for 4 outcomes (asthma-related causes, other respiratory causes, ischemic heart disease, and non-cardiorespiratory causes) from Ontario's real-time syndromic surveillance system and the National Ambulatory Care Reporting System. We also employed different epidemiologic methodologies, including interrupted time-series and case-crossover analyses. RESULTS:After the initial heavy wildfire smoke in early June 2023, daily asthma-related visits increased substantially across Ontario, peaking at a 23.6% increase (95% confidence interval 13.2%-34.9%) at a 1-day lag and lasting up to a lag of 5 days after the start of the smoke episode. The later episode of heavy smoke, despite causing higher exposures, had a reduced effect on asthma-related visits. We did not detect any effect on other outcomes in either episode. These findings were consistent across different methodologies and data sources. Post hoc analysis revealed that asthma-related visits were briefly elevated after the wildfire smoke among children (40% higher), but we observed a more sustained effect among adults (48% higher, lasting 1 week). INTERPRETATION:The 2023 wildfires substantially increased asthma-related emergency department visits in Ontario, with age and timing of exposure being important factors influencing the impact. As wildfires emerge as one of the fastest-growing environmental risk factors globally, future research should identify and evaluate measures to effectively mitigate the acute health impacts of wildfire smoke.

Background: Numerous studies have linked fine particulate matter (PM2.5) to increased cardiovascular mortality. Less is known how the PM2.5-cardiovascular mortality association varies by use of cardiovascular medications. This study sought to quantify effect modification by statin use status on the associations between long-term exposure to PM2.5 and mortality from any cardiovascular cause, coronary heart disease (CHD), and stroke. Methods: In this nested case-control study, we followed 1.2 million community-dwelling adults aged >= 66 years who lived in Ontario, Canada from 2000 through 2018. Cases were patients who died from the three causes. Each case was individually matched to up to 30 randomly selected controls using incidence density sampling. Conditional logistic regression models were used to estimate odds ratios (ORs) for the associations between PM2.5 and mortality. We evaluated the presence of effect modification considering both multiplicative (ratio of ORs) and additive scales (the relative excess risk due to interaction, RERI). Results: Exposure to PM2.5 increased the risks for cardiovascular, CHD, and stroke mortality. For all three causes of death, compared with statin users, stronger PM2.5-mortality associations were observed among non-users [e.g. for cardiovascular mortality corresponding to each interquartile range increase in PM2.5, OR = 1.042 (95% CI, 1.032-1.053) vs OR = 1.009 (95% CI, 0.996-1.022) in users, ratio of ORs = 1.033 (95% CI, 1.019-1.047), RERI = 0.039 (95% CI, 0.025-0.050)]. Among users, partially adherent users exhibited a higher risk of PM2.5-associated mortality than fully adherent users. Conclusions: The associations of chronic exposure to PM2.5 with cardiovascular and CHD mortality were stronger among statin non-users compared to users.

Introduction Work is a key determinant of COVID-19 outcomes, however occupational surveillance is a critical information gap in many countries, including Canada. Understanding the risk of SARS-CoV-2 by occupation can identify high risk groups that can be targeted for prevention strategies. Materials and Methods The cohort includes 1,205,847 former workers compensation (non-COVID-19) claimants (aged 15–65) linked to health databases in Ontario, Canada. Incident cases were defined as either having a confirmed positive polymerase chain reaction (PCR) test in the Ontario Laboratory Information System (OLIS), or an International Classification of Diseases (ICD-10-CA) diagnostic code of U07.1 in hospitalization or emergency department records (February 2020-December 2021). Workers were followed until diagnosis, death, emigration, age 65 or end of follow-up. Sex- and age-adjusted Cox proportional hazards models were used to estimate hazards ratios (HR) and 95% confidence intervals (CI) by occupation, compared to all other cohort members. Analyses were also conducted to examine occupational trends in testing and diagnosis during waves of infection. Results Overall, 80,740 COVID-19 cases were diagnosed among workers during follow-up, of those, 80% were diagnosed with a positive PCR test. Associations were identified between COVID-19 diagnosis and employment in nursing (HR=1.44, CI95%=1.40–1.49), air transport operating (HR=1.61, CI95%=1.47–1.77), textile/fur/leather products fabricating, assembling, and repairing (HR=1.38, CI95%=1.25–1.54), apparel and furnishing services (HR=1.38, CI95%=1.19–1.60), and janitor and cleaning services (HR=1.11, CI95%=1.06–1.16). Restricted analyses where health care workers were omitted from the comparison group strengthened some associations for other high-risk workers. Test positivity ranged between 4–16% across major occupation groups. Risks varied over time and with changes in protective measures in workplaces and in broader communities. Conclusions Elevated risk of SARS-CoV-2 infection in health care, manufacturing, transportation, and service workers were identified, underscoring the importance of including occupational data in COVID-19 surveillance. Occupational trends in severe outcomes and vaccination are also being explored.

[Voir la version anglaise de l’article ici: www.cmaj.ca/lookup/doi/10.1503/cmaj.230592][1] Points clés Une femme de 39 ans a consulté au service des urgences 3 fois en l’espace de 6 semaines pour douleurs abdominales, constipation, nausées et vomissements. Elle avait des antécédents mé

Background:Thirty-five laboratory-confirmed legionellosis cases were reported to the Simcoe Muskoka District Health Unit (Ontario, Canada) between September 27, 2022, and October 15, 2022, resulting in one death and 29 hospitalizations. This article describes the Legionella outbreak and highlights activities for managing the outbreak, including various environmental and infrastructural controls associated with the public health response and some of the unique challenges and potential solutions to mitigate future outbreaks.Methods:All cases of legionellosis were reported to and investigated by the local provincial health unit. Within a 6 km radius around the community, 27 cooling towers (CTs) were identified as potential sources of Legionella. Environmental samples were collected from 19 CTs and a long-term care home.Outcome:Of the 35 cases, 29 (83%) were hospitalized (including three long-term care residents) with two requiring intubation/ventilation. Of the five sputa (clinical isolates) collected from confirmed cases, four tested positive for Legionella pneumophila (one was positive for L. pneumophila serogroup 1-with the same sequence type as one of the CT isolates). Education and recommendations were provided by the local provincial health unit to operators to improve CT operation.Conclusion:Detection and management of community legionellosis outbreaks associated with CTs involve resources and time to properly identify and control risks. Measures for community risk mitigation included coordinating with provincial and community partners, developing methods to rapidly identify CTs as a likely source of infection and applying operational/maintenance/testing standards for CTs to control bacterial growth and minimize the dispersion of contaminated aerosols.

CMAJ | August 8, 2023 | Volume 195 | Issue 30 © 2023 CMA Impact Inc. or its licensors A 39-year-old woman presented to the emergency department 3 times over 6 weeks with abdominal pain, constipation, nausea and vomiting. She had a medical history of hypothyroidism and infertility, and was taking levothyroxine, follitropin alfa injections and folic acid. She lived in a condominium and worked in an office. She did not drink alcohol and was a nonsmoker. She did not have a notable family history. On her third visit to the emergency department, the patient reported abdominal pain, fatigue, nausea and vomiting. Her vital signs were normal. Her hemoglobin level was 67 (normal 115–155) g/L with a mean corpuscular volume of 88.5 (normal 80.0– 98.0) fL. She was admitted to hospital to investigate the anemia and possible gastrointestinal bleeding. Her blood film showed basophilic stippling, slight microcytosis and hypochromasia with no hemolysis. Levels of electrolytes, calcium, magnesium, phosphate, vitamin B12, thyroid-stimulating hormone and liver enzymes were normal. Cultures of blood and urine samples were negative. Results of esophagogastroduodenoscopy, colonoscopy and computed tomography and ultrasonography of her abdomen and pelvis were normal. A bone marrow biopsy to investigate the anemia showed a moderate to marked increase in iron storage. Diagnostic laparoscopy for possible endometriosis showed no visible endometriosis. Biopsies of simple ovarian cysts were sent for pathologic examination. The patient’s abdominal pain improved and her hemoglobin remained higher than 70 g/L after transfusions. Her discharge diagnosis was anemia of unknown cause and possible mild endometriosis. She was prescribed analgesics, laxatives and her usual medications, and was scheduled for follow-up with the internal medicine and hematology services. At the outpatient follow-up with the internal medicine service 2 weeks after discharge, the patient reported improved abdominal pain but ongoing fatigue, shortness of breath, headaches and tinnitus. A urine sample was sent out for porphyria screening. At the second follow-up 4 weeks after discharge, at which point one of the authors became involved (H.A.), her porphyria screen showed elevated levels of coproporphyrin III and δ-aminolevulinic acid. Her biopsies did not show endometriosis. On further inquiry, the patient reported having taken Ayurvedic medications daily to treat infertility for more than a year. Her regimen varied, ranging from a few to a dozen pills daily. She had stopped taking them before her admission to hospital because of the abdominal pain, but had resumed them after discharge. Her blood lead level was 55 (normal < 2) μg/dL. A history of the patient’s occupational and environmental exposure did not reveal other potential sources of lead exposure. The patient stopped her Ayurvedic medications and underwent chelation with 400 mg of succimer (dimercaptosuccinic acid) taken orally 3 times per day for 5 days, then twice per day for 14 days. She was advised to avoid pregnancy until her lead levels had decreased. Lead levels were 19.5 μg/dL shortly after chelation and 12.1 μg/dL 1 year later. The patient reported improving energy and no nausea, vomiting or abdominal pain. Six months after chelation, her hemoglobin level was 119 g/L, with a mean corpuscular volume of 93.1 fL. When the diagnosis of lead toxicity was made, the clinicians contacted Public Health Ontario, a provincial public health agency that provides scientific and technical support to the Ontario government and health care system. Public Health Ontario facilitated testing of 17 visually distinct pills and 2 incense samples provided by the patient. Of these, 11 pills contained lead levels greater than the detection limit and 1 pill contained 129 000 μg/g of lead (about 13% lead by weight), strongly suggesting that the pills were the source of the lead toxicity. Four additional pills contained 7900—33 000 μg/g of mercury. Public Health Ontario involved the local public health unit (Toronto Public Health) and Health Canada, which regulates the importation and sale of natural health products. A joint investigation of the Ayurvedic clinic confirmed the practitioner’s noncompliance with the Natural Health Products Regulations and resulted in the seizure of hundreds of pills.1 Toronto Public Health, consistent with their legislated authority to investigate and manage health hazards, attempted to contact all known customers of the practitioner (about 200 customers) and Practice | Cases CPD

Emissions of fine particulate matter (PM2.5) from human activities have been linked to substantial disease burdens, but evidence regarding how reducing PM2.5 at its sources would improve public health is sparse. We followed a population-based cohort of 2.7 million adults across Canada from 2007 through 2016. For each participant, we estimated annual mean concentrations of PM2.5 and the fractional contributions to PM2.5 from the five leading anthropogenic sources at their residential address using satellite observations in combination with a global atmospheric chemistry transport model. For each source, we estimated the causal effects of six hypothetical interventions on 10-y nonaccidental mortality risk using the parametric g-formula, a structural causal model. We conducted stratified analyses by age, sex, and income. This cohort would have experienced tangible health gains had contributions to PM2.5 from any of the five sources been reduced. Compared with no intervention, a 10% annual reduction in PM2.5 contributions from transportation and power generation, Canada's largest and fifth-largest anthropogenic sources, would have prevented approximately 175 (95%CI: 123-226) and 90 (95%CI: 63-117) deaths per million by 2016, respectively. A more intensive 50% reduction per year in PM2.5 contributions from the two sources would have averted 360 and 185 deaths per million, respectively, by 2016. The potential health benefits were greater among men, older adults, and low-income earners. In Canada, where PM2.5 levels are among the lowest worldwide, reducing PM2.5 contributions from anthropogenic sources by as little as 10% annually would yield meaningful health gains.

Background and aim: Coronavirus disease 2019 (COVID-19) is causing a tremendous health burden globally. Identification of the determinants of COVID-19 severity is important for prevention and intervention. This study aims to explore long-term exposure to ambient air pollution as a potential contributors to COVID-19 severity given its known impact on the pulmonary system. Methods: Using a cohort of all confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cases aged ≥20 years and not residing in a long-term care facility in Ontario, Canada during 2020, we evaluated the association between long-term exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ground-level ozone (O3) and risk of COVID-19-related hospitalization, intensive care unit (ICU) admission and death separately. Participants' long-term exposures to each air pollutant were ascertained based on their residential addresses from 2015 to 2019. We used logistic regression and adjusted for confounding and selection bias using various individual and contextual covariates obtained through data linkage. Results: Among the 151,105 confirmed SARS-CoV-2 cases in 2020, we observed 8,630 hospitalizations, 1,912 ICU admissions and 2,137 deaths related to COVID-19. For each interquartile range increase in exposure to PM2.5 (1.70 µg/m3), we estimated ORs of 1.06 (95% confidence interval (CI): 1.01 to 1.12), 1.09 (95% CI: 0.98 to 1.21) and 1.00 (95% CI: 0.90 to 1.11) for hospitalization, ICU admission and death, respectively. Estimates were smaller for NO2 but larger for O3. Conclusions: In this large population-based study in Ontario during 2020, we found that chronic exposure to air pollution may contribute to severe outcomes following SARS-CoV-2 infection, with stronger evidence found with O3. Keywords: COVID-19 severity, long-term exposure to air pollution, death, hospitalization, intensive care unit admission

Background Long‐term exposure to outdoor fine particulate matter (PM2.5) is the leading environmental risk factor for premature mortality worldwide. Characterizing important pathways through which PM2.5 increases individuals' mortality risk can clarify the PM2.5–mortality relationship and identify possible points of interventions. Recent evidence has linked PM2.5 to the onset of diabetes and cardiovascular disease, but to what extent these associations contribute to the effect of PM2.5 on mortality remains poorly understood. Methods and Results We conducted a population‐based cohort study to investigate how the effect of PM2.5 on nonaccidental mortality is mediated by its impacts on incident diabetes, acute myocardial infarction, and stroke. Our study population comprised ≈200 000 individuals aged 20 to 90 years who participated in population‐based health surveys in Ontario, Canada, from 1996 to 2014. Follow‐up extended until December 2017. Using causal mediation analyses with Aalen additive hazards models, we decomposed the total effect of PM2.5 on mortality into a direct effect and several path‐specific indirect effects mediated by diabetes, each cardiovascular event, or both combined. A series of sensitivity analyses were also conducted. After adjusting for various individual‐ and neighborhood‐level covariates, we estimated that for every 1000 adults, each 10 μg/m3 increase in PM2.5 was associated with ≈2 incident cases of diabetes, ≈1 major cardiovascular event (acute myocardial infarction and stroke combined), and ≈2 deaths annually. Among PM2.5‐related deaths, 31.7% (95% CI, 17.2%–53.2%) were attributable to diabetes and major cardiovascular events in relation to PM2.5. Specifically, 4.5% were explained by PM2.5‐induced diabetes, 22.8% by PM2.5‐induced major cardiovascular events, and 4.5% through their interaction. Conclusions This study suggests that a significant portion of the estimated effect of long‐term exposure to PM2.5 on deaths can be attributed to its effect on diabetes and cardiovascular diseases, highlighting the significance of PM2.5 on deteriorating cardiovascular health. Our findings should raise awareness among professionals that improving metabolic and cardiovascular health may reduce mortality burden in areas with higher exposure to air pollution.

Background: The tremendous global health burden related to COVID-19 means that identifying determinants of COVID-19 severity is important for prevention and intervention. We aimed to explore long-term exposure to ambient air pollution as a potential contributor to COVID-19 severity, given its known impact on the respiratory system. Methods: We used a cohort of all people with confirmed SARS-CoV-2 infection, aged 20 years and older and not residing in a long-term care facility in Ontario, Canada, during 2020. We evaluated the association between long-term exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ground-level ozone (O3), and risk of COVID-19-related hospital admission, intensive care unit (ICU) admission and death. We ascertained individuals’ long-term exposures to each air pollutant based on their residence from 2015 to 2019. We used logistic regression and adjusted for confounders and selection bias using various individual and contextual covariates obtained through data linkage. Results: Among the 151 105 people with confirmed SARS-CoV-2 infection in Ontario in 2020, we observed 8630 hospital admissions, 1912 ICU admissions and 2137 deaths related to COVID-19. For each interquartile range increase in exposure to PM2.5 (1.70 μg/m3), we estimated odds ratios of 1.06 (95% confidence interval [CI] 1.01–1.12), 1.09 (95% CI 0.98–1.21) and 1.00 (95% CI 0.90–1.11) for hospital admission, ICU admission and death, respectively. Estimates were smaller for NO2. We also estimated odds ratios of 1.15 (95% CI 1.06–1.23), 1.30 (95% CI 1.12–1.50) and 1.18 (95% CI 1.02–1.36) per interquartile range increase of 5.14 ppb in O3 for hospital admission, ICU admission and death, respectively. Interpretation: Chronic exposure to air pollution may contribute to severe outcomes after SARS-CoV-2 infection, particularly exposure to O3.

INTRODUCTION:Understanding how different countries have responded to mitigate the risk of severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) transmission in dental offices is important. This article describes the different approaches taken towards optimal fallow periods in Canadian jurisdictions.METHODS:We searched publicly available information from dentist and dental hygiene regulator websites across the 10 provinces and 3 territories in Canada. We also searched for guidance documents on dental associations' websites or through personal communication with government officials. We extracted and tabulated information on fallow period recommendations or guidance, when available.RESULTS:Nine jurisdictions (6 provinces and all 3 territories) acknowledge or provide guidance on fallow periods following aerosol-generating procedures. Among those who have provided guidance regarding a fallow period, recommendations follow the Centers for Disease Control and Prevention guidance if the air changes per hour (ACH) in the dental operatory is known.CONCLUSION:The evidence for deciding on optimal fallow period is limited and still being explored, resulting in substantial variation across Canadian jurisdictions. A focus on developing scientific evidence relevant to dentistry and assimilating existing science is crucial to establishing consistency and uniformity in information to deliver safe oral health care services.

Smokey liquid nitrogen (LN 2 ) infusions are one of the latest eye-catching food trends.With its ability to create fog-like effects and flash freeze foods, LN 2 has become popular for use in ice cream, snacks, and cocktails recently.Although perceived to be harmless, there are incidents of consumers suffering adverse health effects after consuming foods prepared with LN 2 .Thus, a qualitative risk assessment was undertaken to estimate the potential risks to consumers.Through an analysis of gray and scientific literature, case reports related to inhalation, ingestion, and contact with LN 2 were reviewed for relevant information.It was found that inhalation of LN 2 vapors could potentially cause rare, but serious, injuries such as respiratory distress and asphyxia.Ingestion injuries, which typically result after consuming LN 2 before it fully evaporates, often include gastrointestinal barotrauma and rupture.Lastly, when skin or tissues come in contact with LN 2 for more than a short period of time, frostbite can occur.To reduce the risks posed to consumers, it is recommended that (i) vendors are properly trained to handle and serve LN 2 , (ii) patrons are given clear instructions on how to safely consume such treats, and (iii) regulatory agencies put appropriate regulatory interventions into action as needed.

overall well-being of children and youth.Therefore, barring catastrophic circumstances, schools should remain open for in-person learning.

Background: A plethora of performance measurement indicators for palliative and end-of-life care currently exist in the literature. This often leads to confusion, inconsistency and redundancy in efforts by health systems to understand what should be measured and how. The objective of this study was to conduct a scoping review to provide an inventory of performance measurement indicators that can be measured using population-level health administrative data, and to summarize key concepts for measurement proposed in the literature. Methods: A scoping review using MEDLINE and EMBASE, as well as grey literature was conducted. Articles were included if they described performance or quality indicators of palliative and end-of-life care at the population-level using routinely-collected administrative data. Details on the indicator such as name, description, numerator, and denominator were charted. Results: A total of 339 indicators were extracted. These indicators were classified into nine health care sectors and one cross-sector category. Extracted indicators emphasized key measurement themes such as health utilization and cost and excessive, unnecessary, and aggressive care particularly close to the end-of-life. Many indicators were often measured using the same constructs, but with different specifications, such as varying time periods used to ascribe for end-of-life care, and varying patient populations. Conclusions: Future work is needed to achieve consensus ‘best’ definitions of these indicators as well as a universal performance measurement framework, similar to other ongoing efforts in population health. Efforts to monitor palliative and end-of-life care can use this inventory of indicators to select appropriate indicators to measure health system performance.

Background Quantifying the potential cancer cases associated with environmental carcinogen exposure can help inform efforts to improve population health. This study developed an approach to estimate the environmental burden of cancer and applied it to Ontario, Canada. The purpose was to identify environmental carcinogens with the greatest impact on cancer burden to support evidence-based decision making. Methods We conducted a probabilistic assessment of the environmental burden of cancer in Ontario. We selected 23 carcinogens that we defined as “environmental” (e.g., pollutants) and were relevant to the province, based on select classifications provided by the International Agency for Research on Cancer. We evaluated population exposure to the carcinogens through inhalation of indoor/outdoor air; ingestion of food, water, and dust; and exposure to radiation. We obtained or calculated concentration-response functions relating carcinogen exposure and the risk of developing cancer. Using both human health risk assessment and population attributable fraction models in a Monte Carlo simulation, we estimated the annual cancer cases associated with each environmental carcinogen, reporting the simulation summary (e.g., mean and percentiles). Results We estimated between 3540 and 6510 annual cancer cases attributable to exposure to 23 environmental carcinogens in Ontario. Three carcinogens were responsible for over 90% of the environmental burden of cancer: solar ultraviolet (UV) radiation, radon in homes, and fine particulate matter (PM 2.5 ) in outdoor air. Eight other carcinogens had an estimated mean burden of at least 10 annual cancer cases: acrylamide, arsenic, asbestos, chromium, diesel engine exhaust particulate matter, dioxins, formaldehyde, and second-hand smoke. The remaining 12 carcinogens had an estimated mean burden of less than 10 annual cancer cases in Ontario. Conclusions We found the environmental burden of cancer in Ontario to fall between previously estimated burdens of alcohol and tobacco use. These results allow for a comparative assessment across carcinogens and offer insights into strategies to reduce the environmental burden of cancer. Our analysis could be adopted by other jurisdictions and repeated in the future for Ontario to track progress in reducing cancer burden, assess newly classified environmental carcinogens, and identify top burden contributors.