Although most consumers believe that mineral or spring water is healthier than tapwater, the facts don't support this, asserted a report from the British sustainable food and farming group Sustain. Researchers warned of possible hazards associated with bottled water, including extra sodium, benzene, bromate, and the heavy metal antimony. People with high blood pressure or heart problems were advised to check water labels carefully to avoid increasing their sodium intake. According to the UK's Drinking Water Inspectorate, while 99.96% of tapwater meets national purity standards, benzene was found in the Perrier brand and bromate in the Dasani brand of bottled water between 1989 and 2004. Bottles made of polyethylene terephthalate can contain traces of antimony.