Review

Cancer and climate change

Robert A Hiatt, Naomi Beyeler

The acute impact of climate change on human health is receiving increased attention, but little is known or appreciated Lancet Oncol 2020; 21: e519–27
about the effect of climate change on chronic diseases, particularly cancer. This Review provides a synopsis of what is Department of Epidemiology
known about climate change and the exposures it generates relevant to cancer. In the context of the world’s cancer and Biostatistics and
Helen Diller Family
burden and the probable direction we could expect to follow in the absence of climate change, this scoping review of Comprehensive Cancer Center
the literature summarises the effects that climate change is having on major cancers, from environmental exposures (Prof R A Hiatt MD) and
to ultraviolet radiation, air pollution, disruptions in the food and water supply, environmental toxicants, and infectious Institute for Global Health
agents. Finally, we explore the effect of climate change on the possible disruption of health systems that have been Sciences (N Beyeler MPH),
University of California
essential to cancer control practice. We conclude with potential responses and opportunities for intervention. San Francisco, San Francisco,
CA, USA
Introduction and spread of vector-borne diseases, such as dengue. The Correspondence to:
The reality of climate change and its impact on human collapse of fisheries and declining agricultural production Prof Robert A Hiatt, Department
health are no longer in the realm of speculation.1 threaten the global food supply. Water scarcity, drought, of Epidemiology and
Biostatistics, University of
International scientific organisations, such as the Inter­ and poor water quality increase the risk of water-borne California San Francisco,
governmental Panel on Climate Change, have long diseases. Extreme weather events cause death, injury, and San Francisco, CA 94158, USA
predicted the disruptions in planetary ecology and displacement, and disrupt health-care delivery.1,5,6 robert.hiatt@ucsf.edu
human health that the world now faces.2 The Paris Agreement on climate change established a
Health researchers and physicians have long known global target of limiting the temperature rise to less than
about the effects of cli­mate change on infectious diseases 2°C above pre-industrial levels, with efforts to keep
and the conditions caused or exacerbated by limited warming below 1·5°C. These thresholds are widely
access to safe and nutritional food and water.3 However, considered the limits beyond which severe impacts on
the effects on chronic diseases such as cancer are less human and environmental health will occur. Without
clear than the effects on infectious diseases because ambitious climate action, global temperatures are expected
chronic diseases do not occur in close temporal proximity to rise by 3°C or more above pre-industrial levels by 2100.2,7
to the exposures brought about by climate change. This For these reasons, taking action on climate change has
Review provides a synopsis of what is known about been called “the greatest global health opportunity of the
climate change and the trends in the world’s cancer 21st century”.5 Yet environ­mental pollution continues to
burden. We then review the literature on the effects of rise, along with the risk of growing health impacts.
climate change on major cancers and on the health
systems that have been essential to successes in cancer Cancer burden now
control. Global trends indicate that cancer is likely to become the
leading cause of death and principal barrier to increased
Climate change now life expectancy in the 21st century for virtually every
The 5 years from 2015 to 2019 were the warmest 5 years on country in the world.8 According to analysis from the
record.4 Human activities, principally the burning of fossil Global Burden of Disease Study, there were 24·5 million
fuels, have caused global average temperatures to rise by new cases of cancer and 9·6 million deaths in 2017.8
around 1°C above pre-industrial levels.2 This warming has This is a striking increase from 2008, when there were
caused a range of associated climatic changes, including 12·7 million incident cancer cases and 7·6 million
loss of glaciers and polar ice sheets, rise of sea levels, deaths.9 The International Agency for Research on
warming of oceans and ocean acidification, unpredictable Cancer (IARC) GLOBOCAN 2018 statistics align with
changes in rainfall, increased intensity of storms and these estimates.10 A small number of cancer sites account
floods, increased frequency of extreme weather events, for more than half of cancer deaths. In women, the most
and increased frequency and severity of heatwaves, common incident cancers are breast, lung, colorectal,
droughts, and wildfires.3 These environmental changes cervix, and stomach cancers and, in men, the most
have tremendous impacts on human health and global common are lung, liver, stomach, colorectal, and prostate
development.2 Tragically, the effects of climate change cancers.10 But, there is consid­erable heterogeneity in the
disproportionally affect already disadvantaged low-income type of cancers that are most common across countries
communities and countries that are the least responsible and regions of the world, due to differences in genetic
for the causes of climate change. susceptibility, average lifespans, and social determinants
The impacts of climate change on health are wide­ of cancer, including the economic development of a
spread, diverse, and growing rapidly. High temperatures, country, levels of education, human behaviours, and the
poor air quality, and wildfires cause rising rates of strength of health-care systems.11
respiratory and cardiovascular diseases. Rising temper­ What could be expected if the threat of climate change
atures and changing rainfall patterns increase the risk were not looming over us? If the experience of some

www.thelancet.com/oncology Vol 21 November 2020 e519

 Review

Aetiology Prevention Detection Diagnosis Treatment Survivorship

Increased exposure Changes in risk and Changes and disruptions to all aspects of screening, diagnosis, and treatment Disruption in
to cancer risk factors: maintenance of that rely on the function and continuity of health systems, including equipment, psychological
• Air pollution recommended agents, imaging, medical supplies, communications, and surveillance systems support, health
• Chemical toxicants health behaviours: promotion, and
• Ultraviolet radiation • Diet regular follow-up
• Food supply • Physical activity
disruption (access • Sun protection
and quality)
• Infections

Figure 1: Climate change impact across the cancer control continuum

Climate change is likely to affect cancer control actions all along the cancer control continuum from increasing causal factors and modifying behaviours for
prevention and early detection, to disrupting health system factors that underlie early detection, diagnosis, treatment, and survivorship practices.

developed countries is taken as an example of where major disruptions in the infrastructure of health-care
cancer control could go, the future looks optimistic.12 systems for cancer control that could affect all cancers.
Incidence and mortality rates for some major cancers and Observations on the potential effect of climate change
cancer overall are decreasing in high-income countries on human health, including cancer, date back to the
(HICs), such as Australia, New Zealand, the UK, and early 1990s with predictions from Sir Richard Doll16 and
the USA,13–15 largely because of progress in tobacco others17–19 of the adverse effects of the accumulation of
control, improved early detection, and better treatments. greenhouse gases and the associated increasing global
However, these trends are not shared by low-income temperatures. However, most of the literature on the
and middle-income countries (LMICs), where cancer health effects of climate change has come within the past
incidence is associated with increased smoking rates, 10–15 years and is steadily increasing in volume.
excess bodyweight, and physical inac­tivity.13 Nevertheless,
it would be reasonable to expect improvements in LMICs Air pollution and lung cancer
over time as well, given what is understood about the Lung cancer is the primary cause of cancer mortality
underlying reasons for improve­ments in HICs, such as worldwide, and tracheal, bronchus, and lung cancers
cancer control measures against known behavioural together accounted for 2·2 million incident cases
risk factors, effective programmes for early detection, and 1·9 million deaths in 2017.8 Tobacco consumption
improved treatments, and societal policy changes. The remains the number one cause of lung cancer mortality
main environmental and social causes of cancer are but, as success has been achieved in tobacco control, air
amenable to interventions all along the cancer control pollution poses an increasing threat. The severity of air
continuum (figure 1), including actions against the use of pollution is increasing as a result of human activity and is
tobacco products, unprotected exposure to ultraviolet itself contributing to climate change.20,21 The Lancet
radiation, some infectious agents, such as the human Commission on pollution and health established that all
papillomavirus (HPV), toxic environmental chemicals, forms of pollution cause 43% of lung-cancer deaths.22
and dietary modification.13 The current differences Particulate air pollution causes as many as 15% of all lung
between HICs and LMICs can be used as a snapshot of a cancer deaths and deaths attributable to particulate
dynamic process whereby global improvements in cancer pollution have increased by 20% in the past three decades.23
control and reductions in inequities would be expected Multiple comprehensive cohort studies document the
given present day trends and appropriate resources. relationship between the major components of air
However, the consequences of climate change are likely pollution and lung cancer,24 and IARC recognised air
to slow progress in cancer control, as described below. pollution as a carcinogen in 2013.25 The carcinogenic
elements that comprise air pollution include nitrogen
The effects of climate change on cancer dioxide, sulphur dioxide, ozone, particulate matter with a
The principal mechanisms through which climate diameter of 10 micrometres or less (PM10), and PM2·5,26
change is likely to affect cancer control are through although PM2·5 and ozone27 are recognised as the most
causal pathways involving air pollution, exposure to useful indicators for monitoring air pollution. Polyaromatic
ultraviolet radiation, disruptions in food and water hydrocarbons, also designated as carcinogens by IARC,28
supply, exposure to industrial toxicants, and possibly are bound to PM2·5, allowing them to reach deep into the
infectious causes of cancer (figure 2). These effects are lung.20,29,30 Multiple studies have measured these pollutants
associated primarily with cancers of the lung and upper under different cir­cumstances31–34 and one has modelled
respiratory tract, skin, gastrointestinal tract, and liver. the effect of particulate air pollution over the 21st century
However, beyond these causal factors, we can expect worldwide and shown an increase in premature mortality

e520 www.thelancet.com/oncology Vol 21 November 2020

 Review

Greenhouse gas emissions

Climatic changes Drought and wildfire Heat Sea-level rise Extreme weather events

Cancer-related Air pollution Human behaviour Food insecurity Water pollution Infections
effects (particulate, change (outdoor (agricultural yield (infectious and
chemical, wildfires) activity, exercise, and nutritional chemical)
sun protection) quality)

Primary site of cancer Lung Skin Gastrointestinal tract Other?

Influencing factors Health systems (eg, human resources, transportation, service delivery, supply chain), health-care access (accessibility and quality),
social systems and inequities (eg, poverty, migration, displacement, conflict), climate and public health policies

Figure 2: Pathways from climate change to cancer outcomes

Greenhouse gas emissions are resulting in climatic changes, such as rising temperatures, droughts, flooding, extreme weather events, and sea-level rise. In turn,
these changes have cancer-related effects on air pollution, ultraviolet radiation exposure, food insecurity, water pollution, and infections, and will affect human
behaviours, such as physical activity. The primary cancer targets are likely to be the lung and skin, and more general effects of climate change are likely to be related to
poor nutrition and contaminated food and water supplies. Underlying these effects will be the disruption in health systems on which successful cancer control depends.

and lung cancer in all regions except Africa.35 In a meta- Ultraviolet radiation and skin cancers
analysis of a large number of cohort studies over the past An extensive amount of literature exists on the link
25 years, the estimated hazard ratio, adjusted for age, sex, between the increased exposure to ultraviolet radiation
and smoking status, was 1·13 (95% CI 1·07–1·20) per and the increase in squamous cell and basal cell cancers
10 μg/m³ elevation in PM2·5.24 Fewer studies exist on the (now more commonly referred to as keratinocyte cancers)
effects of ozone than on the effects of PM2·5, although and melanomas.41,42 The Global Burden of Disease Study
evidence from one review found no association with lung estimates there were 7·7 million incident cases of
cancer.36 keratinocyte cancer worldwide, with 65 000 deaths and a
Climate change will also increase particulate pollution 33% increase in cases since 2007.8 This increase is
through increasing the risk of wildfires and anticyclonic associated with ageing of the population, but exposure to
conditions (inversions) that increase concentrations of ultraviolet radiation over extended lifetimes is the
pollution and smoke. Wildfire risk is increasing because underlying mechanism. Ultra­violet radiation increases
of drought, rising temperatures, and changes in skin cancers directly through induction of gene
precipitation, along with other human-driven factors mutations and indi­rectly through immunosuppression.43,44
such as land management and development patterns. Melanoma rates worldwide have also increased steadily
Wildfire smoke generates PM2·5 that contains poly­ in recent decades and accounted for more than
aromatic hydrocarbons, benzene, and formaldehyde, 230 000 incident cases and 55 000 deaths in 2012.8 76% of
which are known to be carcinogenic.23 new melanoma cases could be attributed to ultraviolet
Other cancers beyond lung cancer might also be radiation, primarily in North America, Europe, and
affected by air pollution, although the evidence is less Oceania.8,45
convincing than that for lung cancer. Evidence exists for Ozone depletion, resulting from the use of aerosols,
an effect of exposure to environmental chemicals, such such as chlorofluorocarbons and hydrochlorofluoro­
as polyaromatic hydrocarbons37 and nitrogen oxides carbons, has contributed to increasing ultraviolet light
(NOx),38 from air pollution and industrial products on exposure and skin cancer.46,47 However, the 1987
early life development and breast cancer risk. One study Montreal Protocol and its amendments have largely
from China found regional and international associations succeeded in reducing ozone layer depletion and,
between concentrations of PM2·5, other air pollutants, consequently, the likelihood of predicted increases in
and gastric cancer.39 skin cancer by as much as 2 million cases by 2030.48,49 An
Air pollution-related lung cancer will ultimately decline emerging body of literature exists on the potential direct
over time if reductions in emissions can be achieved. A effect of increased temperatures on skin cancer; however,
growing body of literature models the health co-benefits of evidence in humans is inconsistent and the relationship
mitigating policies, such as those that reduce air pollution. remains unclear.50–52
For instance, studies in China show substantial reductions Human attitudes towards sunbathing have long been a
in mortality, including from lung cancer, that would result concern for ultraviolet radiation exposure and skin
from full implementation of China’s climate policies.40 cancer.53 Rising temperatures associated with climate

www.thelancet.com/oncology Vol 21 November 2020 e521

 Review

change result in behavioural changes, such as increasing pollinators (eg, honey bees), and sea-level rise all negatively
time outdoors and shedding of protective clothing, that affect food production and crop yields. Higher concen­
result in more ultraviolet radiation expo­sure41 and skin trations of ambient carbon dioxide also reduce the
cancers than with lower temperatures.54 However, when nutritional content of staple grain crops, including the
temperatures are very high, people spend less time amounts of protein and micro­nutrients.62,63 Rising ocean
outside than they do with small increases in temperature, temperatures and ocean acidification might reduce the
reducing exposure to ultraviolet radiation. So, although productivity of fisheries. In some communities, this
social behaviours are hard to predict, the effects of reduction could affect consumption of fish, and by
human behaviour in response to temperature increases extension omega-3 fatty acids that are protective against
will be a more important factor for skin cancer rates than some cancers.63 Rising sea levels are already affecting food
the increase in ultraviolet radiation itself.41,55 production in some Pacific islands.64 Studies suggest
The effect of greenhouse gases on the ozone layer and climate change also increases the production of myco­
the attendant exposure to ultraviolet radiation have been toxins, such as aflatoxins, which are of aetiological
heterogeneous across the globe.42,56–59 Regions closer to importance for liver cancer, although no evidence of
the equator have higher ambient ultraviolet radiation, increases in hepatocellular cancers associated with climate
which can be exacerbated at high altitudes.60 In Australia, change have been directly attributable to aflatoxins.65–67
where skin cancers account for more than 80% of all Although the overall effects of climate change on
cancers, the Montreal Protocols have led to a decrease in nutrition-related cancers are difficult to ascertain, a
the production of ozone-depleting substances. However, comprehensive modelling study predicted there would
before recovery, increased levels of ultraviolet radiation be 534 000 climate-related deaths worldwide, including
are expected, associated with increased risk of skin deaths from cancer, as a result of changes in food supply
cancers from human behaviours.57 by 2050, such as reduced consumption of fruits and
Increasing malignant melanoma incidence has vegetables.62 This increase in mortality is not offset by a
been tracked in European and North American cancer reduction in red meat consumption—brought about
registries and linked to census and other individual- either by scarcity or mitigation efforts—that could save
level data. One study in the white population of Canada, 29 000 lives by 2050.62 Further, the reduction in colorectal
based on census data and geospatial methods, associated cancer incidence associated with less red meat
summertime exposure to ambient ultraviolet radiation consumption is likely to be confined to HICs,68 whereas
with increased melanoma rates, controlling for age, sex, for populations in LMICs with wide­spread undernutrition
and socioeconomic variables.42 However, this ecological and malnutrition, a reduction in protein sources could
study was not able to characterise exposures at the have a detrimental effect on health.
individual level nor capture variations in exposures over
time. Environmental chemicals
Increased levels of vitamin D resulting from exposure Environmental toxicants are likely to increase with
to ultraviolet radiation have some salutary protective increased industrialisation and chemical production
effects on cancer development.53 Vitamin D, produced by independent of climate change. Coal-fired power plants,
the skin upon exposure to ultraviolet B radiation, has oil and gas extraction, and fracking are all linked to
several positive health effects on musculoskeletal health, pollution in air and water, but climate change could
calcium metabolism, and immune function, but the further increase exposure to these environmental toxins.
balance between DNA damage and skin cancer from Modelling studies of chemical pollutants in glacial
ultraviolet radiation and the beneficial effects of vitamin D meltwater in the Alaskan Arctic and the Swiss Alps show
remains a topic of investigation and diverging opinion.53 elevated concentrations of persistent organic pollutants
that can accumulate in the local fish supply and might
Nutrition, food supply, and cancer increase lifetime cancer risk among populations with high
The extensive studies of diet and cancer have uncovered degrees of local fish consumption.69,70 Modelling studies
many false leads, and intervention trials based on the suggest that public water systems increasingly face higher
best observational data have been frustratingly negative bromide concentrations in source waters from extraction
in terms of effectiveness. However, there is good evidence industry activities, which could increase the lifetime
that healthy diets with whole grains, fruits, and vegetables bladder cancer risk in populations served by sampled
are protective, at least for colorectal and breast cancer, water treatment plants.71 Wildfires might also increase
and the highest risks for cancer are associated with the exposure to toxic chemicals through air pollu­ tion and
adverse effect of adult obesity and excessive alcohol through contamination of ground water. In California,
consumption.61 USA, drinking and ground-water sources were con­
Climate change is affecting the quality and quantity of taminated with benzene following wildfires in 2018.72 In
food production in multiple ways. Rising temperatures, addition, flooding might increase the risk of exposure to
flooding, drought, extreme events (eg, hurricanes, toxic chemicals; in the USA, over 2500 sites handling toxic
typhoons), higher ground-level ozone, declines in chemicals are located in flood-prone areas.73

e522 www.thelancet.com/oncology Vol 21 November 2020

 Review

Infectious causes of cancer probably overwhelm health system capacity as a result

Climate change is linked to increased risk of of surges in injuries, infections, and communicable
Vibrio cholerae infections and vector-borne diseases such diseases, and have implications for cancer care as
as dengue and malaria,3 but links to the infectious causes resources are reallocated to disaster response.
of cancer are not well documented. The prevalences of Major disruptions to hospital functioning and capacity
hepatitis B and C,8 HPV, Epstein-Barr virus, and HIV, occurred following Hurricane Maria in Puerto Rico,81
which play causative roles in cancer, are not directly Hurricane Dorian in the Bahamas, Hurricane Sandy in
related to climate change, although one study in Lesotho New York, USA,27,82 and Cyclone Idai in Mozambique,83
suggested that the response to drought included among other climate-related disasters. After Hurricane
alterations in human behaviours independently asso­ Katrina in New Orleans, USA, there were substantial
ciated with HIV risk through commercial and trans­ delays in oncology treatment due to damaged hospital
actional sex.74 In addition, there has been some infrastructure and radiotherapy equipment, and closure
speculation on the effect of climate change on other of health facilities and cancer treatment units.78 Reduced
infections, such as Helicobacter pylori and its role in access to cancer care and treatment services lasted for
gastric cancer,75 Clonorchis sinensis in cholangiocarcinoma, years after Hurricane Katrina, with substantial effects on
and Schistosoma haematobium in bladder cancer. How­ the health of patients with cancer. 10-year breast cancer
ever, the evidence remains sparse, with some reviews survival was lower for people exposed to Hurricane Katrina
predicting that climate change is more likely to shift the than for those who were not exposed.84
geographical range of these infections rather than expand Sparse evidence on the impact of climate change and
global risk.76 extreme events on cancer progression and survival
suggests a negative effect. A systematic review of natural
Health system effects disasters and cancer found evidence of higher cancer
The most profound challenge to global cancer burden mortality after disasters than before.78 In addition, a
could come from the disruption of the complex and systematic review of the effect of storms and flooding on
integrated health-care delivery systems required for non-communicable diseases including cancer found that
cancer diagnosis, treat­ ment, and care.12 Extreme these weather events increase the risk of disease
weather events such as storms and flooding can destroy progression and death.85 In the USA, researchers found
or damage health-care infra­structure, reducing health- an association between hurricane disasters declared
care quality and availability. These events also interrupt during radiotherapy and overall survival of patients with
service delivery by causing power shortages, disrupting locally advanced non-small-cell lung cancer.86
supply chains, trans­portation, and communication, and
resulting in staff shortages.77 For example, HPV infection Social determinants of cancer
is unlikely to be directly influenced by climate change, Climate change is exacerbating existing social and
but screening, early detection, and vaccination could economic inequities, within and between countries,
easily be disrupted, especially in LMICs where cervical and is leading to rising rates of migration, poverty, and
cancer is most prevalent. Long-term disruptions in conflict, which place people and communities at higher
power and medical supply chains that result from risk than normal for a range of health outcomes.
extreme weather events are a particular threat for Climate change and changing agricultural productivity
patients with chronic medical conditions or who can also negatively affect food distribution, increase
require continuous care for treatment and management food prices, and change food markets, contributing
of their conditions. Radiation oncology services, for to malnutrition and food insecurity. Low-income
instance, are typically unable to operate on backup communities and communities of colour are dispro­
generators;78 therefore, power outages resulting from portionately affected by cancer and have a higher cancer
extreme events or planned disruptions to the power mortality than the rest of the population.11 The
supply, such as that to avert wildfire risk in California, World Bank estimates that climate change will push
can disrupt or delay cancer care. Extreme events also 100 million people globally back into poverty by 2030.87
result in the loss of medical records, which in turn This estimate is on top of other estimates that, by 2050,
affects follow-up care for patients with cancer requiring there will be over 140 million internal climate migrants
highly individualised and complex care and treatment.78 in the regions of sub-Saharan Africa, south Asia, and
Interruptions in cancer treatment and disruptions to Latin America alone.88 Refugees and displaced people
clinical trials79 are associated with poorer treatment and often have little access to health-care services in both
survival outcomes. their home and host countries, and are often diagnosed
Climate events might also reduce access to health-care with more advanced-stage cancer than most people
services, including routine cancer screening, if road when they do present for care.89 Research and action to
and transportation networks are affected. Increased address cancer and climate change must include
temperature even affects the function and reliability of analyses of the adverse effects of climate change on the
some screening immunological tests.80 Disasters will social deter­minants of cancer.

www.thelancet.com/oncology Vol 21 November 2020 e523

 Review

Potential responses and opportunities for Limitations and future research

intervention It is worth noting that the topic of cancer and climate
Although the effect of climate change on cancer remains change is extremely difficult to study because of the
largely unquantified, our Review indicates several path­ complex interplay of exposures and outcomes over time,
ways through which climate change increases cancer multiple confounding factors, and the challenges of
risk, incidence, and mortality. However, various clinical, establishing causal relationships.92 In addition, the
behavioural, and policy solutions can limit climate attribution of either increases or decreases in cancer
change and minimise any potential excess cancer cases incidence to mitigation efforts is challenging given
that might occur as a result. background trends and because the potential salutary
effects of mitigation efforts will take years to realise.
Addressing climate change Thus, the quality of the literature reviewed is limited by
Substantial opportunities exist for policies within energy, the kinds of study designs and approaches that are
agriculture, transportation, health care, and other sectors possible with such complexity. There are no randomised
to substantially reduce greenhouse gas emissions, slow controlled trials, few controlled studies, and a minimum
climate change, and avoid extreme temperature and of well-conducted observational population studies.
sea-level rise, and other climate changes and their Furthermore, cancer, unlike infectious diseases, has a
attendant health effects.12 Such climate change mitigation long latency or incubation period between exposures
policies will also have near-term health benefits beyond and clinical diagnosis, as long as 10–20 years for most
cancer risk reduction. Perhaps most importantly, many solid tumours. Studies that do not take this time lag
climate policies will result in immediate reductions in air into account make a questionable contribution to our
pollution. Meeting the Paris Agreement goals is understanding of the effects of climate change,93 and the
estimated to save 1 million lives every year by 2050 as a effects of mitigation efforts today might not be realised
result of declining air pollution, including reductions in for decades by existing surveillance systems. Finally, it
cancer mortality.90 Policies to increase use of active and might well be that the most lasting and profound effects
public transportation, reduce vehicle emissions, and of climate change are through exposures that occur early
build sustainable agri­ cultural systems can reduce air in life and only manifest themselves decades later. Some
pollution, increase physical activity, and improve diets of these effects could be on the biological mechanistic
and food security.91 level, such as temperature effects on the human
epigenome, and more studies on these mechanisms are
Mitigating exposure to climate-related cancer risk factors needed than have been done so far.94
Although climate change might increase exposure to
cancer risk factors, population health interventions can Conclusion
offset potential increases in cancer risk through indivi­ In the shared worldwide battle to mitigate climate change,
dual and community-wide behavioural and educational the international community is not on track to slow
interventions. For example, individual behaviours such emissions of greenhouse gases. Climate change and
as minimising sun exposure and using sunscreen can trends in air pollution, ultraviolet radiation expo­ sures,
modulate the relationship between climate change and food production and nutrition, environmental toxicants,
skin cancer. Community interventions such as the and perhaps the effects on infectious causes of cancer are
establishment of clean-air shelters can reduce exposure therefore likely to continue and worsen. Even so, it might
to air pollution during wildfire events. Established cancer take decades to study and fully understand the impact of
prevention and early detection activities along with climate change on cancer. Known causes of cancer are
effective health education and promotion efforts, if becoming more prevalent in many low-income countries
implemented proactively and widely, can reduce the and are likely to challenge our ability to maintain and
increased cancer risk that might result from climate achieve global progress in cancer control. Notwithstanding,
change. mitigation efforts are having some success in reducing air
pollution in some parts of the world.
Strengthening health systems and ensuring accessible, At the time of writing, the world is engaged in efforts to
high-quality cancer care combat a pandemic of COVID-19 that has sickened
Preparing climate-resilient health systems, ensuring millions and killed hundreds of thousands of people across
continuity of care during climate events, responding the globe. One consequence of the pandemic has been the
effectively to changes in disease burden, and providing shifting of medical resources away from cancer screening
equitable access to high-quality care are essential to and timely treatment as the focus turns to caring for
protecting human health. In addition, actions by health victims of the infection. The early pandemic response
professionals to influence the social determinants of resulted in a striking reduction in air pollution, showing
global inequities through policy changes and political the potential of extreme measures to result in rapid
leadership are needed to address the social determinants environmental change. However, emissions have since
of cancer amplified by climate change.12 rebounded nearly to prepandemic levels. Nonetheless, it

e524 www.thelancet.com/oncology Vol 21 November 2020

 Review

6 Costello A, Abbas M, Allen A, et al. Managing the health effects of

Search strategy and selection criteria climate change: Lancet and University College London Institute for
Global Health Commission. Lancet 2009; 373: 1693–733.
We did a scoping review of the literature for evidence of 7 International Panel on Climate Change. 2018: Summary for
mechanisms, outcomes, and associations between cancer and policymakers. In: Masson-Delmotte V, Zhai P, Pörtner HO, et al,
eds. Global Warming of 1.5°C. An IPCC Special Report on the
climate change. We searched PubMed and Google Scholar impacts of global warming of 1.5°C above pre-industrial levels
(Feb 14, 2020) using the terms “cancer and climate change”, and related global greenhouse gas emission pathways, in the
“cancer and global warming”, AND “cancer and greenhouse context of strengthening the global response to the threat of
climate change, sustainable development, and efforts to eradicate
gases”. We identified 608 unique articles in English and poverty. Geneva, Switzerland: World Meteorological Organization,
reviewed the titles and abstracts of these papers to identify 2018: 1–24.
77 articles that mentioned some aspect of cancer and climate 8 Fitzmaurice C, Abate D, Abbasi N, et al. Global, regional, and
national cancer incidence, mortality, years of life lost, years lived
change. We then reviewed those articles according to a with disability, and disability-adjusted life-years for 29 cancer
protocol that recorded study information, including the groups, 1990 to 2017: a systematic analysis for the Global Burden of
specific cancer and environmental determinants under study, Disease Study. JAMA Oncol 2019; 5: 1749–68.
9 Ferlay J, Shin H-R, Bray F, Forman D, Mathers C, Parkin DM.
and study methodology (eg, design, exposure measurement, Estimates of worldwide burden of cancer in 2008: GLOBOCAN
outcome assessment). All articles that presented evidence of 2008. Int J Cancer 2010; 127: 2893–917.
climate change on cancer or a cancer precursor were reviewed. 10 Bray F, Ferlay J, Soerjomataram I, Siegel RL, Torre LA, Jemal A.
Global cancer statistics 2018: GLOBOCAN estimates of incidence
20 articles mentioned “climate change” or “cancer” only and mortality worldwide for 36 cancers in 185 countries.
casually and were excluded. However, we included CA Cancer J Clin 2018; 68: 394–424.
11 commentaries or editorials that offered useful perspectives 11 Singh GK, Jemal A. Socioeconomic and racial/ethnic disparities in
cancer mortality, incidence, and survival in the United States,
on cancer and climate change. Most of the selected 57 articles 1950–2014: over six decades of changing patterns and widening
summarised existing knowledge with new insights or were inequalities. J Environ Public Health 2017; 2017: 2819372.
modelling studies that estimated the effects on exposures in 12 Nogueira LM, Yabroff KR, Bernstein A. Climate change and cancer.
CA Cancer J Clin 2020; published online May 18. https://doi.org/
the future. We supplemented this Review with additional
10.3322/caac.21610.
literature that explored the specific pathways from climate 13 Torre LA, Siegel RL, Ward EM, Jemal A. Global cancer incidence
change to cancer. and mortality rates and trends—an update.
Cancer Epidemiol Biomarkers Prev 2016; 25: 16–27.
14 Smittenaar CR, Petersen KA, Stewart K, Moitt N. Cancer incidence
and mortality projections in the UK until 2035. Br J Cancer 2016;
might well be that the lessons from the present pandemic 115: 1147–55.
can be applied to the global challenge of climate change, 15 Marshall DC, Webb TE, Hall RA, Salciccioli JD, Ali R,
including the need for investments in public health and Maruthappu M. Trends in UK regional cancer mortality 1991–2007.
Br J Cancer 2016; 114: 340–47.
health-care infrastructure, research, and intense collective 16 Doll R. Health and the environment in the 1990s.
action on health problems of a global scale. Am J Public Health 1992; 82: 933–41.
Contributors 17 Armstrong BK. Stratospheric ozone and health. Int J Epidemiol
RAH conceived the organisation of the Review, did the literature search, 1994; 23: 873–85.
and was the primary author. RAH and NB reviewed the literature and 18 Longstreth J. Anticipated public health consequences of global
wrote and reviewed major sections of the Review. NB was primarily climate change. Environ Health Perspect 1991; 96: 139–44.
responsible for climate change science and RAH for cancer control 19 Urbach F. Potential health effects of climatic change: effects of
increased ultraviolet radiation on man. Environ Health Perspect 1991;
science.
96: 175–76.
Declaration of interests 20 Yury B, Zhang Z, Ding Y, et al. Distribution, inhalation, and health
We declare no competing interests. risk of PM2.5 related PAHs in indoor environments.
Ecotoxicol Environ Saf 2018; 164: 409–15.
References
1 Haines A, Ebi K. The imperative for climate action to protect health. 21 Jariyasopit N, Tung P, Su K, et al. Polycyclic aromatic compounds
N Engl J Med 2019; 380: 263–73. in urban air and associated inhalation cancer risks: a case study
targeting distinct source sectors. Environ Pollut 2019;
2 Hoegh-Guldberg O, Jacob D, Taylor M, et al. 2018: impacts of 1.5°C of 252: 1882–91.
global warming on natural and human systems.
In: Masson-Delmotte V, Zhai P, Pörtner HO, et al, eds. Global 22 Landrigan PJ, Fuller R, Acosta NJR, et al. The Lancet Commission
warming of 1.5°C. An IPCC Special Report on the impacts of global on pollution and health. Lancet 2018; 391: 462–512.
warming of 1.5°C above pre-industrial levels and related global 23 Matthews-Trigg N, Vanos J, Ebi KL. Climate change and cancer.
greenhouse gas emission pathways, in the context of strengthening In: Bernicker EH, ed. Cancer and society. Cham, Switzerland:
the global response to the threat of climate change, sustainable Springer Nature Switzerland AG, 2019: 11–25.
development, and efforts to eradicate poverty. Geneva: 24 Pope CA 3rd, Coleman N, Pond ZA, Burnett RT. Fine particulate air
Intergovernmental Panel on Climate Change: Geneva, 2019: 275–311. pollution and human mortality: 25+ years of cohort studies.
3 Watts N, Amann M, Arnell N, et al. The 2019 report of The Lancet Environ Res 2020; 183: 108924.
Countdown on health and climate change: ensuring that the health 25 Gibson J. Air pollution, climate change, and health. Lancet Oncol
of a child born today is not defined by a changing climate. Lancet 2015; 16: e269.
2019; 394: 1836–78. 26 Bernard SM, Samet JM, Grambsch A, Ebi KL, Romieu I.
4 US National Oceanic and Atmospheric Administrations’ National The potential impacts of climate variability and change on air
Centers for Environmental Information. Global Climate Report - pollution-related health effects in the United States.
Annual 2019. January, 2020. https://www.ncdc.noaa.gov/sotc/ Environ Health Perspect 2001; 109 (suppl 2): 199–209.
global/201913 (accessed Sept 21, 2020). 27 Malley CS, Henze DK, Kuylenstierna JCI, et al. updated global
5 Watts N, Adger WN, Agnolucci P, et al. Health and climate change: estimates of respiratory mortality in adults ≥30 years of age
policy responses to protect public health. Lancet 2015; attributable to long-term ozone exposure. Environ Health Perspect
386: 1861–914. 2017; 125: 087021.

www.thelancet.com/oncology Vol 21 November 2020 e525

 Review

28 Gao P, Hu J, Song J, et al. Inhalation bioaccessibility of polycyclic 52 van der Leun JC, Piacentini RD, de Gruijl FR. Climate change and
aromatic hydrocarbons in heavy PM2.5 pollution days: implications human skin cancer. Photochem Photobiol Sci 2008; 7: 730–33.
for public health risk assessment in northern China. Environ Pollut 53 Lucas RM, Yazar S, Young AR, et al. Human health in relation to
2019; 255: 113296. exposure to solar ultraviolet radiation under changing stratospheric
29 Gao Y, Yang L, Chen J, et al. Nitro and oxy-PAHs bounded in PM2.5 ozone and climate. Photochem Photobiol Sci 2019; 18: 641–80.
and PM1.0 under different weather conditions at Mount Tai in 54 Piacentini RD, Della Ceca LS, Ipiña A. Climate change and its
Eastern China: sources, long-distance transport, and cancer risk relationship with non-melanoma skin cancers.
assessment. Sci Total Environ 2018; 622–23: 1400–07. Photochem Photobiol Sci 2018; 17: 1913–17.
30 Bandowe BAM, Meusel H. Nitrated polycyclic aromatic 55 Bharath AK, Turner RJ. Impact of climate change on skin cancer.
hydrocarbons (nitro-PAHs) in the environment—a review. J R Soc Med 2009; 102: 215–18.
Sci Total Environ 2017; 581–582: 237–57. 56 Coates SJ, Enbiale W, Davis MDP, Andersen LK. The effects of
31 Hu YJ, Bao LJ, Huang CL, Li SM, Liu P, Zeng EY. Assessment of climate change on human health in Africa, a dermatologic
airborne polycyclic aromatic hydrocarbons in a megacity of perspective: a report from the International Society of Dermatology
South China: spatiotemporal variability, indoor-outdoor interplay, Climate Change Committee. Int J Dermatol 2020; 59: 265–78.
and potential human health risk. Environ Pollut 2018; 238: 431–39. 57 Makin J. Implications of climate change for skin cancer prevention
32 Levy I, Karakis I, Berman T, Amitay M, Barnett-Itzhaki Z. A hybrid in Australia. Health Promot J Austr 2011; 22: S39–41.
model for evaluating exposure of the general population in Israel to 58 Wright CY, du Preez DJ, Millar DA, Norval M. The epidemiology of
air pollutants. Environ Monit Assess 2019; 192: 4. skin cancer and public health strategies for its prevention in
33 Li J, Yang L, Gao Y, et al. Seasonal variations of NPAHs and southern Africa. Int J Environ Res Public Health 2020; 17: e1017.
OPAHs in PM2.5 at heavily polluted urban and suburban sites in 59 Wright CY, Norval M, Kapwata T, et al. The incidence of skin cancer
North China: Concentrations, molecular compositions, cancer in relation to climate change in South Africa. Atmosphere (Basel)
risk assessments, and sources. Ecotoxicol Environ Saf 2019; 2019; 10: 634.
178: 58–65.
60 Harari Arjona R, Piñeiros J, Ayabaca M, Harari Freire F.
34 Zhang J, Yang L, Mellouki A, et al. Diurnal concentrations, sources, Climate change and agricultural workers’ health in Ecuador:
and cancer risk assessments of PM2.5-bound PAHs, NPAHs, occupational exposure to UV radiation and hot environments.
and OPAHs in urban, marine, and mountain environments. Ann Ist Super Sanita 2016; 52: 368–73.
Chemosphere 2018; 209: 147–55.
61 World Cancer Research Fund International. Diet, nutrition, physical
35 Park S, Allen RJ, Lim CH. A likely increase in fine particulate activity, and cancer: a global perspective. https://www.wcrf.org/
matter and premature mortality under future climate change. dietandcancer (accessed Sep 21, 2020).
Air Qual Atmos Health 2020; 13: 143–51.
62 Springmann M, Mason-D’Croz D, Robinson S, et al. Global and
36 Atkinson RW, Butland BK, Dimitroulopoulou C, et al. Long-term regional health effects of future food production under climate
exposure to ambient ozone and mortality: a quantitative systematic change: a modelling study. Lancet 2016; 387: 1937–46.
review and meta-analysis of evidence from cohort studies.
63 Kang JX. The omega-6/omega-3 fatty acid ratio in chronic diseases:
BMJ Open 2016; 6: e009493.
animal models and molecular aspects. World Rev Nutr Diet 2011;
37 Hiatt RA, Brody JG. Environmental determinants of breast cancer. 102: 22–29.
Annu Rev Public Health 2018; 39: 113–33.
64 Sarfati D, Dyer R, Sam FA, et al. Cancer control in the Pacific: big
38 White AJ, Bradshaw PT, Hamra GB. Air pollution and breast challenges facing small island states. Lancet Oncol 2019;
cancer: a review. Curr Epidemiol Rep 2018; 5: 92–100. 20: e475–92.
39 Yin J, Wu X, Li S, Li C, Guo Z. Impact of environmental factors on 65 Cotty PJ, Jaime-Garcia R. Influences of climate on aflatoxin
gastric cancer: a review of the scientific evidence, human producing fungi and aflatoxin contamination. Int J Food Microbiol
prevention, and adaptation. J Environ Sci (China) 2020; 89: 65–79. 2007; 119: 109–15.
40 Wang H, Sanchez L. Health co-benefits from NDC implementation 66 Liew WP, Mohd-Redzwan S, Than LTL. Gut microbiota profiling of
in China. Winnipeg, MB, Canada: International Institute for aflatoxin B1-induced rats treated with Lactobacillus casei Shirota.
Sustainable Development, 2019. Toxins (Basel) 2019; 11: E49.
41 Diffey B. Climate change, ozone depletion, and the impact on 67 Battilani P, Toscano P, Van der Fels-Klerx HJ, et al. Aflatoxin B1
ultraviolet exposure of human skin. Phys Med Biol 2004; 49: R1–11. contamination in maize in Europe increases due to climate change.
42 Pinault L, Bushnik T, Fioletov V, Peters CE, King WD, Tjepkema M. Sci Rep 2016; 6: 24328.
The risk of melanoma associated with ambient summer ultraviolet 68 Dietz WH. Climate change and malnutrition: we need to act now.
radiation. Health Rep 2017; 28: 3–11. J Clin Invest 2020; 130: 556–58.
43 Balato N, Ayala F, Megna M, Balato A, Patruno C. Climate change 69 Miner KR, Bogdal C, Pavlova P, Steinlin C, Kreutz KJ. Quantitative
and skin. G Ital Dermatol Venereol 2013; 148: 135–46. screening level assessment of human risk from PCBs released in
44 Balato N, Megna M, Ayala F, Balato A, Napolitano M, Patruno C. glacial meltwater: Silvretta Glacier, Swiss Alps.
Effects of climate changes on skin diseases. Ecotoxicol Environ Saf 2018; 166: 251–58.
Expert Rev Anti Infect Ther 2014; 12: 171–81. 70 Miner KR, Kreutz KJ, Jain S, Campbell S, Liljedahl A. A screening-
45 Arnold M, de Vries E, Whiteman DC, et al. Global burden of level approach to quantifying risk from glacial release of
cutaneous melanoma attributable to ultraviolet radiation in 2012. organochlorine pollutants in the Alaskan Arctic.
Int J Cancer 2018; 143: 1305–14. J Expo Sci Environ Epidemiol 2019; 29: 293–301.
46 Kaffenberger BH, Shetlar D, Norton SA, Rosenbach M. The effect 71 Regli S, Chen J, Messner M, et al. Estimating potential increased
of climate change on skin disease in North America. bladder cancer risk due to increased bromide concentrations in
J Am Acad Dermatol 2017; 76: 140–47. sources of disinfected drinking waters. Environ Sci Technol 2015;
47 Lin MJ, Torbeck RL, Dubin DP, Lin CE, Khorasani H. 49: 13094–102.
Climate change and skin cancer. J Eur Acad Dermatol Venereol 2019; 72 Los Angeles Times. Cancer-causing chemical taints water after
33: e324–25. deadly Paradise wildfire. April 18, 2019. https://www.latimes.com/
48 van Dijk A, Slaper H, den Outer PN, et al. Skin cancer risks avoided local/lanow/la-me-ln-benzene-poisoning-paradise-20190418-story.
by the Montreal Protocol—worldwide modeling integrating coupled html (accessed Sept 21, 2020).
climate-chemistry models with a risk model for UV. 73 Tabuchi HPN, Migliozzi B, Lehren AW. Floods are getting worse,
Photochem Photobiol 2013; 89: 234–46. and 2,500 chemical sites lie in the water’s path. Feb 6, 2018.
49 Newman PA, McKenzie R. UV impacts avoided by the Montreal https://www.nytimes.com/interactive/2018/02/06/climate/flood-
Protocol. Photochem Photobiol Sci 2011; 10: 1152–60. toxic-chemicals.html?mtrref=www.google.com&gwh=2C5D2487
50 Andersen LK, Hercogová J, Wollina U, Davis MD. Climate change 895C81FCAC5CA3AAF5AC7998&gwt=pay&assetType=REGIWALL
and skin disease: a review of the English-language literature. (accessed Sept 21, 2020).
Int J Dermatol 2012; 51: 656–61. 74 Low AJ, Frederix K, McCracken S, et al. Association between severe
51 van der Leun JC, de Gruijl FR. Climate change and skin cancer. drought and HIV prevention and care behaviors in Lesotho:
Photochem Photobiol Sci 2002; 1: 324–26. a population-based survey 2016–2017. PLoS Med 2019; 16: e1002727.

e526 www.thelancet.com/oncology Vol 21 November 2020

 Review

75 Blaser MJ. Theodore E Woodward award: global warming and the 87 Hallegatte SBM, Bonzanigo L, Fay M, et al. Shock waves: managing
human stomach: microecology follows macroecology. the impacts of climate change on poverty. Washington, DC:
Trans Am Clin Climatol Assoc 2005; 116: 65–75. World Bank, 2018.
76 Blum AJ, Hotez PJ. Global “worming”: climate change and its 88 Rigaud KK, de Sherbinin A, Jones B, et al. Groundswell: preparing
projected general impact on human helminth infections. for internal climate migration. Washington, DC: World Bank, 2018.
PLoS Negl Trop Dis 2018; 12: e0006370. 89 El Saghir NS, Soto Pérez de Celis E, Fares JE, Sullivan R.
77 Salas RN, Jha AK. Climate change threatens the achievement of Cancer care for refugees and displaced populations: Middle East
effective universal healthcare. BMJ 2019; 366: l5302. conflicts and global natural disasters. Am Soc Clin Oncol Educ Book
78 Man RX, Lack DA, Wyatt CE, Murray V. The effect of natural 2018; 38: 433–40.
disasters on cancer care: a systematic review. Lancet Oncol 2018; 90 Markandya A, Sampedro J, Smith SJ, et al. Health co-benefits from
19: e482–99. air pollution and mitigation costs of the Paris Agreement:
79 Hantel A, Abel GA. An action plan for environmentally sustainable a modelling study. Lancet Planet Health 2018; 2: e126–33.
cancer care. JAMA Oncol 2020; 6: 469. 91 Haines A. Health co-benefits of climate action. Lancet Planet Health
80 Rennert G. Colorectal cancer screening: will global warming affect 2017; 1: e4–5.
the accuracy of FIT testing? Gut 2010; 59: 1451–52. 92 Martens WJ. Health impacts of climate change and ozone
81 Zorrilla CD. The view from Puerto Rico—hurricane Maria and its depletion: an ecoepidemiologic modeling approach.
aftermath. N Engl J Med 2017; 377: 1801–03. Environ Health Perspect 1998; 106 (suppl 1): 241–51.
82 Mayer DK, McCabe M. Climate change and cancer care. 93 Hart J. Association between air temperature and cancer death rates
Clin J Oncol Nurs 2013; 17: 231–32. in Florida: an ecological study. Dose Response 2015;
83 Devi S. Cyclone Idai: 1 month later, devastation persists. Lancet 13: dose-response.14-024.Hart.
2019; 393: 1585. 94 Xu R, Li S, Guo S, et al. Environmental temperature and human
84 Bell SA, Banerjee M, Griggs JJ, Iwashyna TJ, Davis MA. The effect epigenetic modifications: a systematic review. Environ Pollut 2020;
of exposure to disaster on cancer survival. J Gen Intern Med 2020; 259: 113840.
35: 380–82.
© 2020 Elsevier Ltd. All rights reserved.
85 Ryan BJ, Franklin RC, Burkle FM Jr, et al. Defining, describing,
and categorizing public health infrastructure priorities for tropical
cyclone, flood, storm, tornado, and tsunami-related disasters.
Disaster Med Public Health Prep 2016; 10: 598–610.
86 Nogueira LM, Sahar L, Efstathiou JA, Jemal A, Yabroff KR.
Association between declared hurricane disasters and survival of
patients with lung cancer undergoing radiation treatment. JAMA
2019; 322: 269–71.

www.thelancet.com/oncology Vol 21 November 2020 e527