An international team of scientists, led by Nanyang Technological
University, Singapore (NTU Singapore), has linked increased air pollution to
an uptick in cases of lung adenocarcinoma (LADC) worldwide. The same study
also concluded an overall lower consumption of tobacco worldwide is
statistically linked to less people contracting lung squamous cell carcinoma
(LSCC).
Lung adenocarcinoma is a type of cancer for which research strongly suggests
that genetic, environmental, and lifestyle factors play a part, while lung
squamous cell carcinoma is often linked to a history of smoking.
This study, done in collaboration between NTU and the Chinese University of
Hong Kong, showed that a 0.1 micrograms per cubic meter (μg/m3)
increment of black carbon, also known as soot, in the Earth's atmosphere, is
associated with a 12 percent increase in LADC incidence globally.
Black carbon is a pollutant that is classified as under PM2.5, and the
research team found that it has increased globally by 3.6
μg/m3yearly from 1990 to 2012.
Meanwhile, a one percent decline of smoking prevalence was associated with a
nine percent drop in LSCC incidence globally. The number of smokers
worldwide decreased by 0.26 percent a year, cumulatively falling by nearly
six percent from 1990 to 2012.
Lung cancer remains the leading cause of cancer with an estimated 1.8
million deaths in 2020, according to CA: A Cancer Journal for Clinicians.
Global statistics have highlighted the trends of lung cancers, but
understanding what may be causing them has been unclear, until the NTU-led
study, which has associated the incidence of the cancers with tobacco
consumption and air pollution.
Professor Joseph Sung, NTU's Senior Vice President (Health and Life
Sciences) and Dean, Lee Kong Chian School of Medicine (LKCMedicine), who led
the study, said, "In our study, we were able to determine that the global
increase of lung adenocarcinoma is likely associated with air pollution. It
had always been unclear, in the past decades, why we are seeing more females
and more non-smokers developing lung cancer worldwide. Our study points to
the importance of environmental factors in the causation of specific types
of lung cancer."
Associate Professor Steve Yim, from NTU's Asian School of the Environment,
who holds an appointment at LKCMedicine, the first author of the study,
said, "Our study provided us with an indication as to the reason behind the
rising trend of lung adenocarcinoma, despite the decreasing trend of smoking
prevalence. Our findings pinpoint the necessity and urgency to reduce air
pollutant emissions, especially black carbon."
The study analyzed data from the World Health Organization from 1990 to 2012
for data on lung cancers, while the dataset for age-standardized smoking
prevalence rates from 1980 to 2012 was derived from the Institute for Health
Metrics and Evaluation, an independent global health research center at the
University of Washington. The statistics on pollution were obtained from
National Aeronautics and Space Administration (NASA). Pollutants that were
analyzed were black carbon, sulfate, and PM2.5.
The results of the study were published in the peer-reviewed academic
journal Atmospheric Environment in November.
Gender and geography have a role to play
The links between lung cancers and black carbon also vary between different
genders across different continents. For instance, the link between the
pollutant and the incidence of both LADC and LSCC was stronger in females
than in males.
Globally, a 0.1 μg/m3 annual increment of black carbon was
linked to a 14 percent rise in LADC in women, compared to nine percent in
men. As for LSCC, the same increase in the pollutant was linked to a 14
percent increase in females, compared to eight percent in the opposite sex.
The study found that the link between air pollutants and LADC varied across
continents. In North America, a 0.1 μg/m3 increment of black
carbon was linked to a ten percent increase in LADC cases, compared to seven
percent in Europe.
In the study, global data demonstrates that the drop in LSCC is more
significant among males, said the researchers, and that the declining trend
coincides with the declining trend of tobacco consumption.
However, despite the overall decreasing trend of tobacco usage, a positive
association between smoking and LSCC was demonstrated for females in Asia,
North America and Oceania, where a one percent increment in the number of
female smokers was associated with a 12 percent increase of the cancer in
those geographies.
Impact of population growth and rising air pollution
The scientists explained that despite lower overall percentage of smokers
worldwide, there were more smokers worldwide due to massive population
growth from 1980 to 2012, resulting in the number of female smokers
increasing seven percent.
The rising incidence of LADC is particularly prominent in Asia, where
emissions of black carbon and sulfate have been on the rise, according to
the scientists.
LADC among males in Asia saw the largest increasing trend, increasing by 24
percent yearly, mainly contributed by the prominent rises in Japan (38
percent yearly) and South Korea (37 percent yearly). For females in Asia,
LADC increased by 25 percent year, similarly, with both Japan (43 percent
yearly) and South Korea (36 percent yearly) showing a clear increasing
trend.
The researchers highlight the prominent trend of air pollution in Asia, in
which black carbon (11.9 μg/m3/year) and sulfate (35.4
μg/m3/year) showed the highest increase worldwide, with South
Korea presenting the largest increase for both pollutants.
The combustion of fossil fuel for power generation or transportation has
long been known as the source of particulate air pollution in most urban
settings. It also worsens climate change by increasing the carbon dioxide
emissions, which cause global warming.
Prof Sung added, "Results of this study should give us fair warning that air
pollution should be better controlled to protect health and avoid premature
deaths from lung cancer or related illnesses, particularly in populations
that live near urban areas, which are known to experience high levels of
pollutant emissions. Air pollution, together with climate change, is one of
the greatest environmental threats to human health. Our findings underscore
the urgent need for further research into how pollutants such as black
carbon and sulfate lead to the development of lung adenocarcinoma, and for
international leaders and experts to look into mitigation strategies for air
pollution."
Assoc Prof Yim added, "While national environmental regulatory bodies
commonly measure and report on the levels of fine particulate matter, our
results pinpoint the importance to measure individual types of particulates,
especially, black carbon. The information would be useful for formulating
effective emission control policies, supporting policies for sustainable
development."
The team plans to carry out further research to investigate the functions of
black carbon and sulfate in the development of LADC, which could lead to new
studies to combat the surge of the cancer. The team also hopes to explore
other pollutants that might be linked to lung cancers.
Reference:
Steve H.L. Yim et al, Rise and fall of lung cancers in relation to tobacco
smoking and air pollution: A global trend analysis from 1990 to 2012,
Atmospheric Environment (2021).
DOI: 10.1016/j.atmosenv.2021.118835
Tags:
Planet and Environment