Blonde residents living in the Swedish town of Anderslov, located in the southern region of the country, all experienced their hair suddenly turning a shade of green.
When this occurred, people were puzzled by the mysterious green locks. Immediate attention was focused on the municipal drinking water in search of excess copper levels, as the metal is known to create a green effect on hair and skin.
After experts tested Anderslov's water in several homes for excessive copper levels, the results showed no problems; this result caused engineers on the case to be stumped.
Further investigation found the cause of the unsolicited green hair was indeed water related, but not in the way they'd initially thought.
The origin of the excess copper was found in the piping used in new homes, but the green dye effect did not occur unless the hot water sat overnight, reported local newspaper Skanskan (courtesy of The Local).
The Local reported when water was left overnight, "the copper suddenly skyrocketed to five or 10 times the normal amount."
Turns out the hot water was causing copper particles to peel off the pipes and the excess went into the water. Older homes were less affected, as the examination determined newer homes lacked coatings on the pipes.
"The samples we took from older houses have lower copper levels," said environmental engineer Johan Pettersson, to local newspaper Skånskan.
The 1,700 residents of Anderslov are being advised to wash their hair in cold water.
Or as The Local puts it, "move to an older house."