Scientists have discovered a shocking link between air pollution and a group of cancers that plague tens of thousands of Americans every year.
The researchers found that exposure to PM2.5 pollution – or particulate matter smaller than 2.5 microns – increases the risk of head and neck cancer (HNC).
Common forms of HNC include throat cancer and oral cancer, with an estimated 71,100 Americans likely to be diagnosed by 2024.
The study found that inhaling PM2.5 increased the risk of developing HNC by 24 percent five years after exposure to this pollutant.
Even within just one year of exposure to PM2.5, the researchers found that the risk of developing HNC increased by 16 percent.
PM2.5 is generated by a variety of industrial processes, including fuel combustion and production, but can be generated indoors by burning candles, using certain cleaning products or air fresheners, and other activities.
Particulate matter can be found everywhere in the US, but PM2.5 pollution is particularly serious in states like California, Georgia and Utah.
Studies have shown that HNC rates are especially high in the Midwest and Southeast. These regional economies rely heavily on manufacturing, agriculture and energy, all of which are major producers of air pollution.
A new study has uncovered a link between air pollution and head and neck cancer (HNC), which tens of thousands of Americans are diagnosed with every year
The harmful effects of particulate matter on human health – including an increased risk of cancer – are well documented.
But now researchers have investigated how inhaling PM2.5 specifically affects the risk of developing HNC.
“Environmental health and personal health are inextricably linked,” said co-author Dr. Amanda Dilger of the Center for Surgery and Public Health and Massachusetts Eye and Ear, in a statement.
Dilger and her colleagues published their findings in the journal Scientific reports on November 12.
The research team, which included several U.S. research hospitals, collected data from the Surveillance, Epidemiology, and End Results (SEER) national cancer database.
The SEER database tracks cancer cases and collects follow-up information on all previously diagnosed patients until their death.
The researchers collected data on HNC cases from 2002 to 2012 and then linked those cases to provincial-level data on PM2.5 pollution, alcohol consumption and smoking over all available years.
The cohort included cancer cases from California, Connecticut, Southeastern Michigan, Georgia, Iowa, Kentucky, Louisiana, New Jersey, New Mexico, Seattle (Puget Sound), and Utah.
Patients had been diagnosed with cancer of the oral cavity, oropharynx, larynx, hypopharynx, sinonasal, and middle ear.
An EPA map shows nationwide PM2.5 levels on November 18, with green dots representing ‘good’ air quality and yellow dots representing ‘moderate’ pollution levels
The analysis showed a significant association between PM2.5 levels and the incidence of HNC, and this association was strongest after a five-year lag period.
This means that the risk of developing HNC increased the most five years after exposure to PM2.5 pollution: by 24 percent.
But exposure to PM2.5 also increased HNC risk over shorter and longer periods.
At the time of exposure (also called a zero-year lag), HNC risk increased by 16 percent, and after twenty years the risk increased by 15 percent.
“These findings shed light on the important role of environmental pollution in upper respiratory and digestive tract cancers, and highlight the need for further awareness, research and mitigation efforts,” said Dr. Stella Lee, senior study author and rhinologist at Brigham and Women’s Hospital , in a statement.
Although the link between PM2.5 exposure and HNC has historically been understudied, the researchers say this type of air pollution is known to be a potent carcinogen.
The International Agency for Research on Cancer (IARC) classifies air pollution, specifically PM2.5, as a carcinogen known to cause cancer in humans, especially lung cancer.
PM2.5 is generated by a variety of industrial processes, including fuel combustion and production
But cells in the head and neck are especially vulnerable to air pollution.
“The link to head and neck cancer is thought to stem from what we breathe and that material that attacks the lining of the head and neck,” said lead author Dr. John Cramer, associate professor of otolaryngology at Wayne State University in Detroit.
“We see many cases where carcinogens hit the body or coalesce to where cancer can occur,” Cramer added.
But breathing air pollution can also lead to other health risks. This study follows research that found a link between exposure to air pollution and the increased incidence of miscarriages in Baoji, China.
There are several theories about why air pollution can cause miscarriage, including disrupting pregnancy hormones, causing harmful inflammation in the mother, and negatively affecting fetal development.
As researchers delve deeper into the many ways air pollution harms human health, they are also pushing for better air quality standards to mitigate the effects of these hazardous substances.
“Our study highlights the need to improve air quality standards to reduce the risk of developing cancer, including head and neck cancer,” said Dr. Dilger.