Spring heat dome, a blow to RFK, Jr.’s health agenda, SpaceX Starlink milestone

Kendra Pierre-Louis: For Scientific AmericanIt is Science quicklyMy name is Kendra Pierre-Louis, I’m replacing Rachel Feltman. You are listening to our weekly summary of scientific news.

If you live in much of California or the southwest United States, you’ve probably said to yourself, “It’s hot in here.” Last week, a heat dome centered on this region, but expected to extend east to Mississippi and north to southern Montana, created unprecedented mid-March temperatures that reached triple digits in some places.

To demystify this first heat wave and its links to climate change, we have Andrea Thompson, senior life sciences editor here at SciAm.

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Thanks for joining us, Andrea.

Andrea Thompson: Thank you for inviting me.

Pierre-Louis: Spring has just begun, and much of the Southwest and parts of the Western United States are cooking; they cook. What is happening?

Thompson: Yeah, so, you know, this follows a month of March that was really wild in terms of weather in general. You know, March is the start of spring, so it’s a transitional weather season anyway as the sun rises and the jet stream over the United States shifts. So there are masses of warm and cold air colliding, resulting in things like tornadoes and extreme weather, as we’ve seen.

What’s happening here is this: it’s a high pressure area, or a ridge in weather terms, and it’s incredibly intense, especially in March. And when there are these ridges, temperatures skyrocket.

So this is an incredibly huge, incredibly extreme, incredibly persistent heat event, especially at this time of year.

Pierre-Louis: So we know that with heat events, there’s kind of two big problems, right? One is the heat itself, like 100 degrees [Fahrenheit, or about 37.8 degrees Celsius] it’s only 100 degrees. But if you come from a period where maybe it wasn’t that hot and now you’re hit with 100 degrees, the body has a really hard time adjusting.

Thompson: That’s right, the body acclimatizes as temperatures gradually warm up until spring, and then we arrive at summer. Whereas right now we place summer right at the end of winter. [Laughs]and bodies are not ready for that.

Pierre-Louis: So there’s definitely a risk that, you know, some people will get very sick or even die from this heat wave.

Thompson: Yes, there’s definitely that potential, and there are heat advisories and extreme heat warnings in some places, you know things like that.

Pierre-Louis: All of this is also happening at a time when, I believe, much of the West is arid. So what will this combination of very hot weather and already somewhat dry conditions do?

Thompson: Much of the West, especially the Rockies, has been quite dry this winter and the winter has been very warm. In fact, the western United States has more distinct wet and dry seasons, and they rely heavily on the snowpack that accumulates during the winter and gradually melts in the spring and summer. But there is no [Laughs] There’s already a lot of snow left because it’s so warm, and much of the precipitation that has fallen this winter has fallen as rain. Much of the remaining snowpack will melt due to this event. And the soil and rivers may not always be able to absorb all of that amount, so some of that amount will be lost.

You know, so you’re creating a drier spring and summer, which significantly increases the risk of a really bad wildfire season. The largest wildfire in Nebraska history is currently occurring there. So, you know, there’s a big concern, and particularly in some of the high mountain forests where we haven’t seen a ton of wildfires in the last few years, that that could change with the drought and the snowpack being so low.

Pierre-Louis: This naturally raises the question of climate change. How does this factor into everything we see?

Thompson: So basically, climate change means that when there is a big heat event, it will be hotter than it was in decades past because the Earth’s base temperature is higher. So it’s kind of… it makes the extremes even more extreme.

There is some evidence that there can be this kind of “weather whiplash” in the West, where you go from a period of relative humidity to a period of extreme drought quite quickly. And it’s bad for wildfires because you built this very green area [Laughs] the grasslands and the forests, and then all of a sudden they dry up and there’s even more fuel for the fires.

And what’s really interesting is the other weather that happened: There was a really, really huge snowstorm in the Midwest. We had a few tornadoes. And in Hawaii, there was what’s called a “Kona Low,” which is a low pressure system. This brought a ton of rain and flash flooding to the islands. It actually makes this heat event stronger, which is just a fascinating way to connect these weather events that you wouldn’t think are related.

Pierre-Louis: We move from heatwaves to policy changes regarding childhood vaccines.

Last Monday, a federal judge issued a ruling that, at least for now, blocks the January from the Centers for Disease Control and Prevention decision to modify the childhood vaccination schedule. The agency had reduced the number of diseases it recommended children 17 to 11 years old should be vaccinated against. Among the vaccines the agency removed were those that protected against hepatitis A and B, rotavirus and RSV.

The decision follows a lawsuit filed by the American Academy of Pediatricsalong with several other plaintiffs, against the U.S. Food and Drug Administration, the CDC, the National Institutes of Health, and the U.S. Department of Health and Human Services. Health Secretary Robert F. Kennedy, Jr., and other officials are also named as defendants.

The plaintiffs, who initially filed their suit in July 2025, allege that the defendants’ actions, quote, “sow confusion and harm public health, willfully ignore and contravene required processes, and ignore decades of established science.” Specifically, the lawsuit highlights actions such as tightening recommendations for COVID-19 vaccines as well as the mass firing of members of the Advisory Committee on Immunization Practices, or ACIP. In doing so, the plaintiffs claim the agencies and officials violated the Administrative Procedure Act, which dates back to 1946 and controls how federal agencies develop and publish regulations.

ACIP has traditionally been an independent, nonpartisan, science-backed federal advisory committee charged with providing vaccine recommendations. In June, HHS removed all 17 sitting members of the ACIP. Many members chosen by the Secretary of Health to replace them do not have training in vaccines and immunology and/or are criticism of vaccines. HHS also circumvented the ACIP with its January decision to revise the childhood immunization schedule.

In his decision Last week, a Federal Court judge concluded that the removal of former ACIP members and bypassing the committee to make the new vaccine recommendations had, quote, “undermined the integrity of the committee.” The judge added that the government’s failure to consult the ACIP represented, quote, “an abandonment of the technical knowledge and expertise embodied by this committee.”

The decision blocked the appointment of the 13 ACIP members selected by the HHS secretary, saying the move likely violated federal law. As a result, the ACIP meeting originally scheduled for last Wednesday and Thursday was postponed.

Continuing the theme of children’s health, anyone who has spent time with young children knows that objects (toys, other people’s hands, clothes) tend to end up in their mouths. Research presented at the American Chemical Society’s spring meeting this week suggests that when it comes to children’s fast fashion, this could be of particular concern. That’s because all of the children’s shirt samples tested by the presenters exceeded federal limits for lead in children’s products.

Limitations exist because lead is a neurotoxin that can seriously damage a child’s nervous system, especially if exposed before the age of six. Exposure can lead to cognitive impairment, behavioral problems, and speech and developmental delays.

The researchers, led by Kamila Deavers of Marian University, sampled 11 shirts, all of which exceeded the allowable lead limit of 100 parts per million. Shirts in brighter colors like red and yellow tended to contain higher levels of lead. Lead acetate is sometimes used as a cheaper way to help dyes adhere to fabrics, researchers say.

The researchers also simulated what would happen if a child sucked or chewed the fabric and found that exposure would exceed the FDA’s safe limits for lead consumption.

This is not the first study of this type. A Greenpeace Germany 2025 Report reviewed clothing, including children’s clothing, from fast fashion retailer Shein. He found items exceeding safety limits for lead, as well as other dangerous chemicals. But this latest work has focused on children’s clothing without focusing on a single retailer.

And finally, head to space.

Last Tuesday, SpaceX crossed the threshold of around 10,000 satellites in low Earth orbit. The company, which launched its first Starlink satellites in 2019, now represents more than 60% of satellites in orbit, but its competitors are hot on its heels. Amazon Leo plans to launch more than 7,500 satellites, while Chinese government-backed companies Guowang and Qianfan are targeting 13,000 and 15,000 satellites, respectively.

SpaceX satellites have helped some 10 million users connect to the Internet in areas as remote as rainforests and battlefields. But it comes at a price: the night sky. Satellite interference is already hampering astronomy as celestial objects become harder to see, a situation that will only get worse as more satellites take up space in orbit.

That’s all for today! Tune in Wednesday to learn how artificial intelligence can change pure mathematics.

Science quickly is produced by me, Kendra Pierre-Louis, with Fonda Mwangi, Sushmita Pathak and Jeff DelViscio. This episode was edited by Alex Sugiura. Shayna Posses and Aaron Shattuck check in on our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more recent and in-depth scientific news.

For Scientific American, This is Kendra Pierre-Louis. Have a good week!