I'm glad this is getting attention. I was in Germany in July and watched a ~1h documentary about the working conditions there. Confirming what is written in the Guardian. The image I saw in the documentary were extreme. No access to clean water, no access to working bath rooms, no paying. They're also lured into coming there being promised a better life and once they're there they realize it but it's too late.

There has also been a report on it in March from Spiegel:

http://www.spiegel.de/sport/fussball/wm-2022-internationaler...

I usually dont' quote BILD, but they say the workers get paid ~0.78 Cent (EUR) an hour:

http://www.bild.de/sport/fussball/wm/arbeiter-werden-wie-skl...

No air conditioning when it's often over 50 deg. celsius (~122 Fahrenheit). This could explain the many hear failures noted in the article.