A recent leak at the nation’s underground nuclear waste dump in New Mexico has caused 13 workers to test positive for radiation. The workers were working aboveground the night of the leak, and it is not yet clear what,if any, health effects will come about.

Workers at the Waste Isolation Pilot Plant inhaled “plutonium and americium, which if lodged in the body bombards internal organs with subatomic particles for the rest of the person’s lifetime.” Sounds like tons of fun.

The leak, which occurred on February 14 in a repository half a mile below the surface of the earth, is the first at the site since it started accepting plutonium-contaminated waste from nuclear bomb facilities a decade and a half ago. The WIPP contains more than 80,000 cubic metres of contaminated material, including clothing and construction equipment.

The Department of Energy says that detailed air monitoring put the radiation levels above ground below unsafe levels, and that a filtration system to keep 99.7 percent of contamination below ground worked. These failsafes have not been tested under live conditions, however, so their efficacy is under close scrutiny.

The radiation amount is not negligible (any radiation level above zero is probably worth investigating) , but it is also certainly not cause for widespread panic. According to Scientific American:

 The agency estimated that a person at one of its above-ground monitoring stations would have sustained a cumulative radiation exposure of 1 millirem – ten times less radiation than that delivered during a typical chest X-ray.

It is not clear exactly what cause the leak. It is possible that falling debris damaged a container, but because nobody was below ground when it happened or has been below since, investigators can only speculate. Nine days prior to the incident, a truck in the plant’s mines caught fire, but officials say that and the leak are unrelated.