From something called Reponse Source (seems to be a press release) comes this incipit:

Following a warning from scientists linking asthma in children to indoor swimming pools, Allergy UK today awarded its “Seal of Approval” for a new alternative to chlorine.

The award comes as hot tubs, spas, swimming pools and inflatable pools become the “must have” accessory as Britain swelters in the sun.

The technology was discovered by the Greeks, and is used today by NASA for keeping drinking water clean in space. It works by deactivating bacteria, rather than aggressively killing it.

Instead of chlorine, Pristine Blue uses a natural copper sulphate solution at levels permitted for use in drinking water. It has been approved in the US for use in all 52 States, and is used there in 600,000 pools and spas.

... the company's website doesn't seem to mention the Greeks. Anyone know whence comes this claim?