Tag Archives: #pollutant

Scientists Identify Severe Asthma Species, Show Air Pollutant As Likely Contributor (Medicine)

For the first time, an analysis identifies non-atopic childhood asthma as more than a set of symptoms, but a distinct disease, driven by early exposure to Benzo[a]pyrene from fossil fuel combustion

Asthma afflicts more than 300 million people worldwide. The most severe manifestation, known as non-Th2, or non-atopic childhood asthma, represents the majority of the cases, greater than 85%, particularly in low-income countries, according to Hyunok Choi (https://health.lehigh.edu/faculty/choi-hyunok), an associate professor at the Lehigh University College of Health (https://health.lehigh.edu/). Yet, whether non-Th2 is a distinct disease (or endotype) or simply a unique set of symptoms (or phenotype) remains unknown.

“Non-Th2 asthma is associated with very poor prognosis in children and great, life-long suffering due to the absence of effective therapies,” says Choi. “There is an urgent need to better understand its mechanistic origin to enable early diagnosis and to stop the progression of the disease before it becomes severe.”

Studies show that nearly 50% of the children whose asthma is poorly controlled are expected to emerge as severe adult cases. Yet, a one-size-fits-all treatment approach, currently the norm for asthma, is ineffective and, says Choi, and partially responsible for asthma’s growing economic burden.

“The primary reason for lack of therapeutic and preventive measures is that no etiologic, or causal, driver has ever been identified for the non-Th2 asthma,” says Choi.

Now, for the first time, an epidemiological study, led by Choi, has shown that not only is non-Th2 a distinct disease, its likely inducer is early childhood exposure to airborne Benzo[a]pyrene, a byproduct of fossil fuel combustion. Choi and her colleagues are the first to demonstrate air pollution as a driver of the most challenging type of asthma, the severe subtype which is non-responsive to current therapies.

The team describes their results in an article (https://rdcu.be/cip0w) recently published online in Environmental Health Journal called “Airborne Benzo[a]Pyrene May Contribute to Divergent Pheno-Endotypes in Children.” (https://rdcu.be/cip0w) Additional authors: Miroslav Dostal, Anna Pastorkova, Pavel Rossner, Jr., and Radim J. Sram from the Department of Genetic Toxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czech Republic.

What is termed asthma is an umbrella word for multiple diseases with common symptoms. Asthma has been broadly classified as two major sets of symptoms: T helper cell high (Th2-high) and T helper cell low (non-Th2). Th2-high is associated with early-childhood allergies to common pollutants such as pet dander, tree pollens, or mold. In contrast, non-TH2 is not related to an allergic response. The non-Th2 type, marked explicitly by being non-allergy-related, is far less understood than the TH-2 type and could transform into severe or difficult to treat type.

“The identification of non-Th2 asthma as a distinct disease, with early exposure to Benzo[a]pyrene as a driver, has the potential to impact tens of millions of sufferers, since this would make it possible to intervene before the onset of irreversible respiratory injuries,” says Choi.

The team tested two comparable groups of children from an industrial city, Ostrava, and the surrounding semi-rural area of Southern Bohemia, in the Czech Republic: 194 children with asthma and a control group consisting of 191 children. According to the study, Ostrava is an industrial city with a high level of coal mining activities, coal processing, and metallurgical refinement. The district-level ambient mean for Benzo[a]pyrene at the time of their investigation November 2008) was 11-times higher than the recommended outdoor and indoor air quality standard.

Not only was elevated exposure to Benzo[a]pyrene associated with correspondingly elevated odds of non-Th2 asthma, it was also associated with depressed systemic oxidant levels.

“Contrary to the current body of evidence supporting adult onset of non-atopic asthma, our data suggest for the first time that the lung function deficit and suppressed oxidative stress levels during early childhood are critical sentinel events preceding non-atopic asthma,” says Choi.

Reference: Choi, H., Dostal, M., Pastorkova, A. et al. Airborne Benzo[a]Pyrene may contribute to divergent Pheno-Endotypes in children. Environ Health 20, 40 (2021). https://ehjournal.biomedcentral.com/articles/10.1186/s12940-021-00711-4 https://doi.org/10.1186/s12940-021-00711-4

Provided by Lehigh University

Extreme UV Laser Shows Generation of Atmospheric Pollutant (Chemistry)

Hokkaido University scientists show that under laboratory conditions, ultraviolet light reacts with nitrophenol to produce smog-generating nitrous acid.

An advanced laser technique has allowed researchers to observe, in real-time, the decomposition of a pollutant into atmospheric nitrous acid, which plays a key role in the formation of ozone and photochemical smog. The technique, described by Hokkaido University researchers in The Journal of Physical Chemistry Letters, could be used in a wide range of applications.

Nitrophenols are a type of fine particulate matter found in the atmosphere that form as a result of fossil fuel combustion and from forest fires. It is hypothesised that light interacts with nitrophenols and breaks them down into nitrous acid; atmospheric nitrous acid is known to generate the hydroxyl radicals responsible for ozone formation. Too much ozone and nitrogen oxides lead to the formation of an atmospheric haze called photochemical smog, which can cause respiratory illnesses. Until now, there has been no evidence for the decomposition of nitrophenol into nitrous acid by sunlight.

Hokkaido University applied physicist Taro Sekikawa and colleagues developed a new probing technique to observe the process in real-time. They then compared their measurements with theoretical quantum chemistry calculations.

“Our study showed that irradiation of o-nitrophenol with sunlight is one of the direct causes of nitrous acid production in the atmosphere,” says Sekikawa.

The team developed an advanced laser technique that involves exciting nitrophenol with a 400 nanometer-wavelength laser light and then shining very short, very fast pulses of ultraviolet light on it to see what happens. Specifically, they used extreme UV light, which has very short wavelengths, shone in femtoseconds, which last a millionth of a billionth of a second. The whole process measures the energy states and molecular changes that occur as the nitrophenol compound decomposes over time.

In the atmosphere, sunlight breaks down nitrophenol to form nitrous acid (HONO), which leads to photochemical smog (Taro Sekikawa).

The scientists found that nitrous acid begins to form 374 femtoseconds after the nitrophenol is first excited by light. The decomposition process involves distortion of the shape of the nitrophenol molecule by light irradiation and changes in its energy states, ultimately leading to the formation of nitrous acid.

“Photoelectron spectroscopy with extreme ultraviolet light is expected to have a wide range of applications as a method for measuring chemical reactions,” says Sekikawa. “It could be used, for example, to understand the mechanism by which ultraviolet rays inactivate viruses at the molecular level, and to understand other chemical reactions that take place in the atmosphere.

Associate Professor Taro Sekikawa (Photo: Taro Sekikawa).


The work was financially supported by Ministry of Education, Culture, Sports, Science and Technology (MEXT) Quantum Leap Flagship Program (Q-LEAP; JPMXS0118068681), Japan Science and Technology Agency (JST) Core Research for Evolutional Science and Technology (CREST; JPMJCR15N1, JPMJCR1902) and KAKENHI (19H01814), and the Photoexcitonix Project in Hokkaido University.

Featured image: Extreme ultraviolet femtosecond pulse light source and photoelectron spectrometer, key instruments used in the experiment (Photo: Taro Sekikawa).

Reference: Yuki Nitta, et al. Real-Time Probing of an Atmospheric Photochemical Reaction by Ultrashort Extreme Ultraviolet Pulses: Nitrous Acid Release from o‑Nitrophenol. The Journal of Physical Chemistry Letters. January 4, 2021. DOI: 10.1021/acs.jpclett.0c03297

Provided by Hokkaido University