What is SAR?
A SAR level stands for the "specific absorption rate" measured by the rate at which energy from wireless technology is absorbed into the body. Both the EU and US FCC regulate the SAR levels in electronic devices. Since these electromagnetic waves, such as RFID, WiFi, and Bluetooth, issue in a certain amount of radiation, there is cause for concern if these SAR levels are too high. One hears about these levels most often with cell phones, but many are concerned with the growing number of devices that rely on wireless technologies, including Apple iPad SAR levels.
In the US, the FCC requires that devices perform with a SAR level of less than 1.6 watts per kilogram (W/kg) taken over 1g of tissue. The EU regulators enforce a limit of 2 W/kg, but over 10g of tissue. Scientific studies have not conclusively linked SAR levels (or even cell phone use) to damage and health issues in humans, but that is not to say that there is no evidence to suggest that such exposure doesn't have effects, especially long-term effects, in humans.
iPad SAR Levels
The iPhone, for example, has SAR levels ranging from .79 W/kg to 1.38 W/kg, all depending on which model one gets (iPhone 3G is the highest). The Apple iPad on average has an iPad SAR level of 1.04 W/kg. The iPad SAR level varies from frequency to frequency, ranging from .74 to 1.19 W/kg. These are the US FCC levels which are taken over 1g of tissue. The EU levels are going to be similar.
So, if you've been worried about SAR levels, you can rest easy knowing that the Apple iPad is not emitting more RF radiation than a smart phone. Plus, you're not holding the device up to your head either, which is a good thing. The display emits more radiation than a cell phone because of the larger screen, but not more than most notebooks or desktops, but that's a topic for another article.
The long and short of it is that iPad SAR levels are well within the limits allowed by regulatory bodies around the world. I think you would be better served checking the SAR levels of your cell phone since some of the smartphones in particular have levels right at the maximum allowed by the FCC. So, you can keep on downloading those apps and editing your photos on the go with your Apple iPad; SAR levels are, by all current accounts, very safe.
The following references were used to gather some of the technical information related to SAR levels and the governmental bodies that regulate such levels in electronic devices around the world.
Cnet on Cell Phone SAR Levels: https://reviews.cnet.com/cell-phone-radiation-levels/
Wikipedia on SAR levels: https://en.wikipedia.org/wiki/Specific_absorption_rate