The amount of X-rays needed to detect trace amounts of lead with a handheld device are probably more dangerous than the lead itself if such an device is used on

The amount of X-rays needed to detect trace amounts of lead with a handheld device are probably more dangerous than the lead itself if such an device is used on a daily basis. There is a reason why your dentist goes to stand behind a wall when you she takes an X-ray of your teeth. If you would have a sample with 10% lead, the amount of X-ray used during for taking an X-ray of your teeth might be enough to measure its concentration within a few 1% accuracy, but if you are talking about 1ppm (and that is far above the 15ppb that is considered safe) you need a lot more X-ray to get a good enough reading. Measuring exact contents with XRF is difficult if you do not have homogeneous samples due to all kinds of complicated effects where the XRF from one element interacts with the XRF of another element. To get within 1% accuracy you often need a controlled (vacum) environment and callibrate your instrument with a set of standards at regular interfalls. At least that is how it was 20 years ago when I developed software for a company that produced high-end industrial XRF measurement devices.