Air, Ash, and Astronomy: How Tiny Pollutants and Giant Telescopes Define the Future

How PM2.5 wrecks respiratory airways

With most of the world population subject to harmful levels of air pollutants, air pollution is stated to be the second leading risk factor that could lead to death globally. However, how air pollution affects human health and mortality remains poorly understood, rendering treatment strategies largely symptomatic.

In a study recently published in The Journal of Clinical Investigation, a multi-institutional research team led by the University of Osaka, Japan, has unravelled the mechanism by which exposure to air pollutants of particle size ≤ 2.5 micrometres (PM2.5) cause airway dysfunction.

Most air pollutants—for example, dust, vehicle exhaust, and wildfire smoke—belong to the PM2.5 category and, when inhaled, cause severe airway damage resulting in respiratory distress. To understand how exactly air pollutant particles affect the respiratory system, the researchers performed a series of experiments on mice. After exposing mice to environmental pollutants, their respiratory tracts were examined for changes in structure and function.

“We found that PM2.5 air pollutants negatively affect mucociliary clearance, a major protective mechanism in the respiratory tract,” said the lead author, Noriko Shinjyo. Mucociliary clearance basically involves trapping pollutants in a sticky mucus and then sweeping the pollutants out of the airways with hair-like projections called cilia.

The researchers found that oxidative injury in the airways caused by the pollutants facilitated the formation of lipid peroxide–derived aldehydes, which damaged the protective cells in the airway, including airway cilia. With the damaged airway cells and cilia no longer able to move debris and pollutants out of the airways, the risk of infection is enhanced.

The team also explored how to restore normal cellular function and reverse damage. The researchers investigated the expression of one gene from the ALDH family known to protect the body against harmful aldehydes, to see whether it countered the effect of airway pollutants.

“Aldehyde dehydrogenase (ALDH1A1) is an enzyme that plays an important role in protection against aldehydes. We used experimental mice that lacked ALDH1A1 to investigate the impact of air pollutants without the gene,” explained Yasutaka Okabe, senior author. “As expected, the mice had impaired cilia formation and function and high levels of aldehydes.”

The team concluded that the absence of ALDH1A1 left the cells at a higher risk of serious respiratory infection when exposed to air pollutants. It was also found that drug-enhanced ALDH1A1 levels improved the mice’s mucociliary function in response to pollutants. The finding thus implied a potential therapeutic target, namely the enzyme ALDH1A1.

Vera C. Rubin Observatory will start showing spectacular images of the sky from June 

Astronomers around the world are eagerly waiting for the clock to strike 11 am EDT (8:30 pm IST) on June 23 when the Vera C. Rubin Observatory, located atop the El Peñón peak of the 2,682-metre-high mountain Cerro Pachón in northern Chile, will showcase online its first spectacular images of the sky.

The observatory is named after the American astronomer Vera Florence Cooper Rubin (1928–2016), who pioneered work on galaxy rotation rates. This study led her to discover the discrepancy between the predicted and observed angular motion of galaxies, which has been cited by astronomers as evidence for the existence of dark matter.

The chief objective of the observatory’s telescope, called the Simonyi Survey Telescope (or SST, named after the private donor-couple Charles and Lisa Simonyi), is to carry out a synoptic astronomical survey, the Legacy Survey of Space and Time (LSST), using its camera, which is the largest digital camera ever built. The LSST camera was built as a multi-institutional project at the SLAC National Accelerator Laboratory, Stanford, California, over a seven-year period. It was shipped to the observatory site in Chile exactly a year ago and was installed in March 2025.

The SST is a wide-field reflecting telescope with an 8.4 m primary mirror. The optics uses a novel three-mirror design that allows the telescope to deliver sharp images over a very wide 3.5^o-diameter field of view. The images will be recorded by the mind-boggling 3.2 gigapixel charge-coupled device (CCD) imaging LSST camera—roughly the same number of pixels as 260 modern cell phone sensors—which itself is of the size of a small car and weighs about 3 tonnes.

The observatory is jointly funded by the National Science Foundation and the Department of Energy of the US government.

To produce an image of the night sky, the Rubin Observatory’s large mirrors first collect the light arriving from the cosmos. After bouncing through the mirrors, the light gets focussed by the camera’s three lenses onto the image sensors. When taking an image of the sky, the camera uses one of six different coloured filters, u, g, r, i, z, and y, ranging from ultraviolet (u), which is outside the human range of vision, through visible colours (g, r, i), and outside the human range of vision in the other direction into the infrared (i, z, y).

The filters are housed in a carousel so that they can be easily switched during observations. However, the geometry of the carousel only allows it to hold five filters at once. The sixth filter is housed in a special storage stand separate from the camera, and a device called the filter loader is used to exchange a particular filter when needed with one in the carousel. 

Compared with filters in normal cameras, these filters are big, each is 75 cm across. A sophisticated machine called the auto-changer is capable of changing the filters in under two minutes.

One would need hundreds of ultra-high-definition TV screens to display a single image taken by this camera. Its sensor needs to be kept extremely cold (about −100°C) to limit the number of defective (bright) pixels in images.

These images and videos will be the first of many that Rubin will release over the course of the next decade as the camera and telescope conduct a sweep of the entire visible southern sky every three to four nights. In doing so, the Rubin Observatory’s telescope will produce the most detailed time-lapse view of the cosmos ever.