I can't help but wonder exactly what they're measuring - that is WHICH pylons. As I understand it, some emergency services radio nets are subcontracted to mobile telco's - and some of their GSM masts are put to dual use - weak GSM signals, AND the rather stronger signals used by the ambulance service. There's a degree of coflation here. "Studies show that GSM masts don't cause illness". Maybe so - but what about the OTHER stuff they've got bolted on to some of their masts?
It's not unlike passive smoking and car exhaust. Both contain carbon monoxide. But lock yourself in a garage and start chain -smoking Silk Cut, and it's NOT going to have the same effect as revving-up your Ford Fiesta. Concluding that the CO output from cigarettes doesn't lead to rapid death and cherry-red eyeballs (telltale sign of CO poisoning) doesn't mean that sharing a sealed garage with a car isn't going to kill you. But a similar implication seems to be present. Phone masts are probably safe - provided that's ALL they're being used for. The jury's out on dual-use masts.