Fake solar eclipse glasses have flooded the market, including on Amazon, ahead of the celestial event across north America on 21 August, leading to warnings from NASA.
The National Aeronautics and Space Administration Agency has recommended just five manufacturers that meet the ISO 12312-2 standard for eclipse glasses, warning that unsafe versions are being distributed by "unscrupulous companies".
NASA said that buying eclipse glasses off Amazon did not ensure their safety.
"We do have some confirmed reports of glasses being sold on Amazon by various vendors that are not genuine and that are not made from well-known manufacturers with documented proof of their identification," Rick Fienberg, spokesperson for the American Astronomical Society (AAS), told The Verge.
"Please check the safety authenticity of viewing glasses to ensure they meet basic proper safety viewing standards," NASA said on its website.
Either side of a total eclipse, where the sun disappears behind the moon, and during a partial eclipse it is dangerous to look directly at the sun, which can cause permanent damage to the eyes.
However, special eclipse glasses or solar filters have been developed that allow keen sky-watchers to witness the celestial event. These glasses are ultra dark, made from specific materials, and meet specific certification standards that block more than 99.99 per cent of the sun's light (double that of regular sunglasses), as well as ultraviolet rays and infrared light.
NASA's basic criteria for eclipse glasses include: an ISO 12312-2 certification; the manufacturer's name and address printed on the product; and not be older than three years and not have scratched or wrinkled lenses.
But demand for such glasses ahead of the eclipse has seen production boom – particularly of dodgy, substandard versions.
According to Quartz, there are around 140 listings on Amazon for eclipse glasses.
A Quartz investigation of the search listings, found that "only 16 claimed to use lenses manufactured by one of the NASA-approved companies… and none of the 25 sponsored listings were made by a NASA-approved company".
In addition, "of the 140 Amazon listings reviewed by Quartz, 119 of 140 claimed to have the proper ISO certification. Some even say they are just as good as the NASA-approved manufacturers, but haven't gotten approval yet", the publication reported.
Meanwhile, only 33 of the listings identified the manufacturer's name, and some of those that did were questionable companies that claimed they manufactured the glasses in Western countries such as Canada but further investigation showed the country of manufacture was actually China, Quartz said.
According to the American Astronomical Society there has been a rush on getting AAS/NASA approval for glasses, but in many cases, complete and correct documentation has been lacking, which has raised concerns.
Andrew Lunt of TSE17, one of the NASA-approved manufacturers, has voiced his concerns about the growing marketplace for eclipse glasses. In an interview with Quartz, he said he had discussed his concerns with Amazon and the need to keep counterfeits off the platform.
He has also purchased glasses from various Amazon sellers and tested them to "get a sense of the scope of the problem". He told the publication he had come across a lot of counterfeits, which were ripping off the intellectual property but weren't found to be overly dangerous when tested.
It is understood that Amazon is updating its policy for eclipse glasses and will now be requiring sellers to provide details of safety, accredited ISO certification and origin of manufacture in order to gain approval to sell on the marketplace.
The NASA-approved companies making eclipse glasses are: American Paper Optics, Rainbow Symphony, Thousand Oak Optical, TSE17, and Baader Planetarium (AstroSolar Silver/Gold film only).