Manila, June 17 -- An environmental watchdog on Tuesday warned parents and students against the sale of insulated steel tumblers painted with high levels of lead, a toxic substance especially hazardous to children.

A day after the official opening of classes in public schools, volunteers from the EcoWaste Coalition disclosed they bought some of these tumblers sold on the streets of Binondo and Quiapo in Manila.

The tumblers were subjected to X-Ray Fluorescence (XRF) analysis, a scientific method used to quickly detect elemental composition.

Findings revealed that 11 unbranded tumblers had exterior coatings containing lead concentrations well above the legal limit of 90 parts per million (ppm).

A plain yellow-painted 600 milliliter (ml...