SAR stands for "Specific Absorption Rate" and means that a part of the radio waves is transformed into heat. It is measured in such a way as to make continual use of the mobile phone possible without any negative health effects. The value is set at two Watts/kg. This warms the body by a maximum of 0.1 degree, which is comparable to the warming caused by light athletic activity.
Low SAR-rates do not automatically mean more security. What is more important is the distance between the mobile phone and the closest base station. With growing distance between the phone and the base station the appliances automatically increase their transmitting power to avoid interruption. This is why highly developed networks mean fewer emissions.
SAR Values (FMK)