Is Wireless LAN(WLAN) is harmful to human body?  

i don't think LAN network is harmful to human body, and there is no side effects.as you said cellphones(mobiles) are harmful if you use them more often..and research's proven this fact.

somewhat.but don't worry about that, the normal wlan signal is not strong enough to harm your body.there's almost no side effect to your health .don't worry about that. :)