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June 26, 2025—The vaccine additive thimerosal is safe. Plus, retracing an ancient oceanic trek, and astronomers spot an eruption of gases on the solar system's largest comet. —Andrea Gawrylewski, Chief Newsletter Editor | | Expert paddlers in the dugout canoe recreating the ancient journey from Taiwan to the Ryuku Islands. Yousuke Kaifu | | | | |
Thimerosal, a compound used in some vaccines as a preservative that has been around since the 1930s, has been historically misunderstood. The compound is made from ethylmercury, but due to limited research in the 1990s, people equated it with methylmercury, which is more easily absorbed by neurological tissues and builds up in the body (and the main source of which is fish). In the late 90s, thimerosal was removed from childhood vaccines due to its supposed health risks. Turns out, ethylmercury is quickly and easily cleared by the body, and since thimerosal's removal from childhood vaccines, numerous studies have found that it does not increase the risk of any neurodevelopmental or other health issues. Why this matters: Secretary of Health and Human Services Robert F. Kennedy Jr. added a discussion on thimerosal to this week's meeting of the Advisory Committee on Immunization Practices, which is part of the CDC. That committee reviews and votes on several vaccine recommendations. Today the committee ruled that Americans should not receive flu vaccines containing thimerosal, despite many studies that have found it is safe.
What the experts say: Removing thimerosal from childhood vaccines was the right decision, say both Neal Halsey, an infectious disease pediatrician at Johns Hopkins University, and Ryan Marino, a medical toxicologist at University Hospitals in Cleveland. But opinions in the medical community differ on how the removal affected public perception of the compound. "We want to reduce any exposure to mercury," Marino says, "but I think, in retrospect, appeasing people's fearmongering without any evidence may have backfired because now people think it was taken out because of problems when it was never shown to cause any issues." —Andrea Tamayo, newsletter intern
| | Agronomist Jiraporn Inthasan compares the carbon balance of different farming methods by taking direct readings of how carbon is trapped and released in the soil. "In this mountainous landscape, it takes two of us to carry the trace-gas analysis equipment out into the field to take these measurements," she says. But it's worth it to build an understanding of agriculture's climate impacts beyond the emission of greenhouse gases. "We aim to capture the whole picture," says Inthasan. Nature | 3 min read | | Read every article that interests you with a subscription to Scientific American. We offer special discounts for Today in Science readers! | | - From 2003 to 2022, face-to-face socializing among U.S. men fell by 30 percent. For teenagers, it was a staggering 45 percent. An estimated 12 percent of Americans report having no close friends, a fourfold increase since 1990, reports Kim Samuel, a research fellow at Oxford University. "The absence of meaningful social bonds can literally recalibrate the body's physiological mechanisms toward greater stress and illness," she says. "Social isolation weakens our civic 'immune system,' fueling polarization and making us more susceptible to authoritarian impulses." | 5 min read
| | Experts were right to worry about the societal effect of removing thimerosal from vaccines in the 90s. One of the many kinds of cognitive biases is called an anchoring bias, the tendency of people to cling to ("anchor") the first piece of information they hear about something. Even if many subsequent studies showed the safety of thimerosal, many people may have assumed the reason it was removed was because it was dangerous. That first impression has hung on for quite some time. (By the way, I recommend scrolling through the Wikipedia page for all the different kinds of biases. It's amazing that anything gets done in society given the myriad quirks of human cognition.) | | —Andrea Gawrylewski, Chief Newsletter Editor
With contributions by Andrea Tamayo | | | | |
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