Medical Technology

Doctors as Trusted Messengers

On a recent Friday, oncologist Christine Berg, MD, devoted 3 hours to a webinar about electrification of heavy- and medium-duty trucks in Maryland.

It’s not the way most cancer specialists choose to spend their time. But Berg, who is board certified in medical oncology, radiation oncology, and internal medicine, has made air pollution her current focus. Through organizations such as the Public Employees for Environmental Responsibility, she is working to raise awareness of the huge impact it can have on cancer.

“I think oncologists can make a difference,” she said.

That’s why Berg took a keen interest in a recent study by ProPublica, the nonprofit journalism organization, that identified previously ignored “hot spots of cancer-causing air.” While the ProPublica report gives an incomplete picture of airborne carcinogens, it puts an important spotlight on industrial air pollution, Berg and other experts say.

Relying on data from the Environmental Protection Agency’s Risk-Screening Environmental Indicators (RSEI), ProPublica researchers estimated the effects of industrial air pollution around the country and found problems the EPA overlooked, they reported. “The EPA collects data on each individual facility, but it doesn’t consider the excess cancer risk from all of the facilities’ combined emissions,” reporter Lylla Younes and colleagues wrote. “ProPublica did.”

The ProPublica team produced a map of cancer-causing industrial air pollution hot spots. They estimated that 256,000 people in the United States live in areas where incidences of cancer caused by air pollution exceed the EPA’s upper limit of acceptable risk.

While some of the spots are scattered around the country, they are concentrated along the Gulf Coast of Texas and Louisiana. For example, near the Equistar Chemicals Bayport Chemical Plant in Pasadena, Texas, ProPublica calculated the increased risk of cancer at 1 in 220, “46 times the EPA’s acceptable risk.” (The agency defines an acceptable risk as less than a 1 in 10,000 chance of developing cancer.)

Almost all the hot spots with the highest level of risk are in southern United States “known for having weaker environmental regulations,” the report said.

The researchers also identified race as a risk factor. In predominantly Black census tracts, they estimated the risk from toxic air pollution is more than double the risk in predominantly White census tracts. It attributed this pattern to deliberate policies of redlining that segregated neighborhoods and to zoning ordinances that encouraged industry in communities of color.

Measuring Risk Not Straightforward

In response to a query from this news organization, an EPA spokesperson provided a statement saying the RSEI data are not intended for the purpose used by ProPublica. “RSEI does not provide a risk assessment (e.g., excess cancer case estimates),” the statement said. The RSEI data are poorly suited to this purpose because they use “worst-case assumptions about toxicity and potential exposure where data are lacking, and also use simplifying assumptions to reduce the complexity of the calculations,” the statement said.

Instead, the data are meant as a kind of index to compare one place to another, or show changes over time, the agency said. In this way, it can prompt regulators to investigate further. “A more refined assessment is required before any conclusions about health impacts can be drawn.” The agency is working on just such a refined approach, per the EPA statement.

That’s not just bureaucratic stonewalling, said Stan Meiberg, PhD, MA, a former EPA official and director of graduate studies in sustainability at Wake Forest University in Winston-Salem, N.C. “To say that you can speak with great precision, that the risk of individuals getting cancer is 1 in 100, may be a little overstating the date on which that statement is based.”

Risk estimates are improving as citizens gain access to more sophisticated monitoring devices, he said. And the primary point of the ProPublica report, that the EPA has underestimated risk by looking at individual sources of pollution rather than combining them, is not an original one, Meiberg said. “This is an issue that’s been kicking around for quite some time.”

Still, it’s one that demands attention. EPA regulations have succeeded in reducing the overall risk from industrial air pollution over the past few decades. “But there remain areas of particular geographic concentrations,” he said. “And the ProPublica article hit two of them, which have been the subject of discussion for many years, the Houston Ship Channel area and the Baton Rouge to New Orleans industrial corridor where you have a significant proportion of all the chemical petrochemical industry in the United States.”

Improvements in containment of the pollutants, and changes to the industrial processes that produce them, can also help reduce exposure. These changes should occur in the context of dialogue within the communities exposed to the pollution, Meiberg said.

The Role of Cancer-Causing Airborne Particulate Matter

But even if measures are perfectly implemented, Joan Schiller, MD, will not breathe easy. An adjunct professor of oncology at the University of Virginia in Charlottesville, Schiller has researched the role of airborne particulate matter in causing cancer, a correlation barely mentioned in the ProPublica analysis, she pointed out.

Particulate matter contains a wide range of toxic substances, she said. Researchers have focused on particles 2.5 microns in diameter, or PM 2.5. Some studies have indicated that it’s responsible for one in seven deaths from lung cancer, Schiller said. “Air pollution also causes lung cancer in never smokers, people who’ve never smoked, not just in smokers.”

Power plants and automobile traffic may be more significant sources of PM 2.5 than industry, and wildfires have recently emerged as increasingly important source, a result of climate change and poor forest management, she said.

PM 2.5 doesn’t affect just lung cancer, said Alexandra White, PhD, an investigator at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C. “My work, as well as work of others, is increasingly suggesting that air pollution is also related to breast cancer risk, in particular, air pollution that is arising from traffic related forces.” And more research is needed on other cancers, she said. “I think that the lack of findings of other cancer sites reflects a lack of study.”

Other pollutants not analyzed in the ProPublica report are also correlated to cancer risk. In a recent meta-analysis, researcher Stephan Gabet, PhD, PharmD, and colleagues at the University of Grenoble, France, estimated that 3.15% of new breast cancer cases in that country could be attributed to nitrogen dioxide and 2.15% to PM 10.

Sources of nitrogen dioxide, PM 2.5, and PM 10 in France include automobile traffic, inefficient wood-burning stoves, and coal-burning power plants in neighboring countries, Gabet said.

A good approach to reducing pollution from road traffic is the implementation of low-emission zones that prohibit the most polluting vehicles, he said. But a 2019 United Kingdom government study found that brake wear, tire wear, and road surface wear account for 72% of the PM 10 and 60% of the PM 2.5 pollution from road traffic, suggesting that a transition to electric vehicles won’t fix the problem. Better yet, is “the promotion of active modes like walking, cycling, etc., because like this, you can bring additional health gains due to the increase in physical activity,” he said.

Oncologists can help their patients reduce their exposure to air pollution, Schiller said. “If you have lung cancer, air pollution will hasten your demise. It makes you sicker. Oncologists should be telling their patients about this and advising them to move away from air pollution if possible, and also making sure they know to monitor the health of the air.”

On days when air pollution is high, patients may want to avoid exercising outdoors, or stay indoors altogether, Berg said. Air purifiers and N95 masks may also help.

And physicians can make a difference by speaking out in their communities, Schiller said. She is inviting oncologists to join a new group, Oncologists Understanding for Climate and Health. Through this group or on their own, oncologists can speak to their local legislatures or city councils in support of measures to reduce pollution, she said. “Doctors are trusted messengers.”

Berg disclosed affiliations with Grail, Mercy BioAnalytics and Lucid Diagnostics.

This article originally appeared on, part of the Medscape Professional Network.

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