Can you provide me with articles about that? Afaik the general scientific consensus is that as long as it's not shoving out >100watts or is releasing EM radiation on an ionizing band (UV and higher), then it's pretty harmless.
Can you warm up a chicken with wifi? Yeah, but afaik a signal that strong would probably already violate various international treaties regarding radio communications long before it got strong enough to have a noticable affect on the chicken.
Think about how many watts your microwave needs to cook food. That's the amount of power it takes to heat up food using EM radiation that's been roughly tuned with the intention of penetrating and heating physical matter by generating friction between water molecules. If I understand the article, the iPhone is putting out less than 6 watts. That's almost nothing. Should there be a limit? Yeah, but to my knowledge, you'd start accidentally jamming communication frequencies around you long before it became a threat to personal health.