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All 12 astronauts who walked on the Moon during NASA’s Apollo missions experienced “lunar hay fever” due to exposure to Moon dust, according to discussions on Hacker News referencing historical mission reports.

Lunar regolith, the fine dust covering the Moon’s surface, caused irritation to the eyes, throat, and lungs of Apollo astronauts after they tracked it back into their spacecraft. The dust clung to their suits and equipment during extravehicular activities and was inhaled or came into contact with mucous membranes when they removed their helmets inside the lunar module.

The dust was described by astronauts as having a smell similar to gunpowder once brought into the pressurized cabin and exposed to moisture. This odor resulted from the reactive nature of the lunar soil, which has not been altered by atmospheric or weathering processes like Earth soil.

Harrison Schmitt, the only professional geologist to walk on the Moon during Apollo 17, reported particularly strong symptoms, including nasal congestion and throat irritation, which he attributed to the dust’s chemical reactivity. Other astronauts, including Charles Duke and John Young, also noted similar respiratory discomfort after moonwalks.

Unlike terrestrial dust, lunar regolith is composed of sharp, angular particles formed by micrometeorite impacts over billions of years. These particles remain electrostatically charged due to the Moon’s lack of atmosphere and constant exposure to solar wind, making them adhere tightly to surfaces and increasing their potential to cause irritation.

Studies of returned lunar samples have shown that the dust contains reactive compounds such as nanophase iron, which can generate hydroxyl radicals in the presence of moisture — a property that may contribute to its effects on human tissue. This reactivity is absent in Earth-based dust analogs due to oxidation and weathering.

The health effects observed during the Apollo missions were temporary and resolved after the astronauts returned to Earth. However, the experience has informed ongoing research into the risks of lunar dust for future long-duration missions under NASA’s Artemis program.

Current efforts to mitigate lunar dust hazards include testing materials for spacesuit coatings, developing air filtration systems for lunar habitats, and studying electrostatic repulsion techniques to prevent dust accumulation. Researchers are also investigating whether magnetic or thermal methods can be used to deflect or remove charged particles from equipment and surfaces.

Understanding the properties and effects of lunar regolith remains critical for ensuring astronaut safety and equipment functionality in future missions, particularly as plans advance for sustained human presence on the Moon.