Studies Show Air Pollution Raises Risk of Non-Lung Cancers, Impacts Dementia Patients’ Mental Health

Exposure to air pollution is linked with a variety of health issues, including a higher risk of respiratory infections, heart disease, and lung cancer. Two recent studies have highlighted other health risks, one related to brain health and one to other types of cancer.

The first study, published in Environmental Epidemiology, investigated the impacts of chronic exposure to fine particulate air pollutants (PM2.5) and nitrogen dioxide (NO2) on breast, prostate, colorectal, and endometrial cancer incidence in older adults. It found that both types of pollution exposure were linked with a higher risk of colorectal and prostate cancers. The researchers say this underscores the need to better address air pollution.

Yaguang Wei, the study’s first author and research fellow in the Department of Environmental Health at Harvard T.H. Chan School of Public Health, says, “Our findings uncover the biological plausibility of air pollution as a crucial risk factor in the development of specific cancers, bringing us one step closer to understanding the impact of air pollution on human health. To ensure equitable access to clean air for all populations, we must fully define the effects of air pollution and then work towards reducing it.”

To conduct the study, the team looked at Medicare data collected between 2000 and 2016 on patients 65 and older who had no cancer diagnoses during the first 10 years of the study period. The researchers broke the patients down into groups based on which of the four types of cancer they developed, with between 2.2 million and 6.5 million in each group.

To gauge impacts of air quality on these groups, the researchers used air pollution data to create a predictive map of fine particulate air pollutants and nitrogen dioxide concentrations across the contiguous U.S. They then looked at the patients’ ZIP codes to help determine their pollutant exposure over a 10-year period.

The findings showed that chronic exposure to both types of pollution were linked with an increased risk of colorectal and prostate cancers, while nitrogen dioxide exposure was associated with a decreased risk of breast cancer, and neither appeared to play a role in endometrial cancer incidence.

In areas where air pollution levels were well below national standards and the composition of fine particulate air pollutants remained stable, there were stronger associations with breast cancer risk. At lower levels for both pollutants, there was also a stronger link with endometrial cancer risk.

Other findings suggested a higher risk of all four types of cancer with nitrogen oxide exposure on those with a higher average BMI, as well as a higher risk of prostate and breast cancers among Black Americans with fine particulate air pollutant exposure.

As the study indicates there are issues even at pollution levels below World Health Organization guidelines, the researchers say standards may need to be tweaked.

Joel Schwartz, senior author and professor of environmental epidemiology, says, “The key message here is that U.S. air pollution standards are inadequate in protecting public health. The Environmental Protection Agency recently proposed stricter standards for PM2.5, but their proposal doesn’t go far enough in regulating this pollutant. Current NO2 standards are also woefully inadequate. Unless all of these standards become much, much stricter, air pollution will continue to result in thousands of unnecessary cases of multiple cancers each year.”

Another recent study published in BMJ Mental Health highlighted a different health risk of air pollution: Higher use of mental health services by dementia patients.

The research, led by scientists from King’s College London, focused on PM2.5 and NO2, as well. The findings showed that in a large area of London with heavy traffic, high levels of air pollution were linked to more use of community mental health services among those with dementia.

The study involved more than 5,000 people aged 65 and older, 54% of whom had Alzheimer’s and 20% of whom had vascular dementia, with the rest having another or an unspecified form of the disease. The data were drawn from people who had been diagnosed between 2008 and 2012 and included nine years of community mental health service use data. Air pollution figures were taken from quarterly published estimates and focused on where the patients lived.

The study showed that within the first year of monitoring, higher pollution exposure was linked with increased use of these health services, and use went up as exposure increased, particularly with NO2. Patients with vascular dementia were the most impacted. Regarding NO2, those with the highest exposure were 27% more likely to use the services than those with the lowest exposure. For PM2.5, the figure was 33%.

These associations continued five to nine years into monitoring, particularly in those with vascular dementia.

Though it’s an observational study that does not show that the pollution causes the use of these health services, the researchers project that the use would decrease if PM2.5 and NO2 were at the recommended World Health Organization levels. With PM2.5 at these levels, it’s estimated that mental health service use could go down by 13% each year, while that figure could be 38% lower if NO2 were at recommended levels.

The authors write, “The reduction in air pollution and particularly NO2 through public health interventions such as the expansion of ultra-low emission zones could potentially improve functioning and disease trajectories for people with dementia.

“Reducing pollutant exposure might reduce the use of mental health services in people with dementia, freeing up resources in already considerably stretched psychiatric services.”

To read more of that study, click here.