So, how to make a cheap enough device? You don't need great accuracy - 20% accuracy is fine for this. You need very high sensitivity in the detector because you don't want to generate a lot of x-ray energy in a device hold for household use.
To be practical the device would have to emit so little energy as to be basically harmless even if used on a person. (Low power, but also short duration.)
You can also just test children's blood. That is much more direct and would catch the problem whether it's the paint at home, the water, the paint at grandma's house, etc...
The problem is cumulative, so if you're testing everyone early you greatly limit the damage.
Massachusetts mandates that every child is tested for lead in the blood between 8 and 12 months of age, then at 2 years and at 3 years. Every pediatrician does the tests automatically at the normal checkups. And our rates of lead poisoning are much better than most other states with old houses.
In some places, like NYC, there's often a legal presumption that ALL paint contains lead. It seems that for legal purposes detection is not always the central issue.
"All paint in a pre-1960 multiple
dwelling unit where a child under age 6 resides and in the common areas of such multiple
dwellings is presumed to be lead paint. A lead-based paint hazard is any condition in a
dwelling or dwelling unit where a child under age 6 resides that causes exposure to lead
from lead-contaminated dust, from lead-based paint that is peeling, or from lead-based
paint that is present on chewable surfaces, deteriorated subsurfaces, friction surfaces, or
impact surfaces that would result in adverse human health effects."
Maintenance and remediation become central in these cases, I think. A government-approved technology that lowers the cost and risk of remediation would be a big winner.
I can't help but add: I wonder what Donald Trump does to maintain and remediate the lead in his NYC buildings...
Sorry you were downvoted. I gave you an upvote before my initial response.
You may have been downvoted because your response may have seemed a little snarky to some. While your suggestions make sense they are not necessarily practicable or economically feasible in all cases. People are pretty sensitive when it comes to the health their children and wants what's best even when they cannot provide it.
No, if the human race is doomed, it's because ignorant people think it's okay to leave children exposed to known toxic substances.
No amount of "supervision" is going to keep a child from consuming lead paint. Children do not get lead poisoning because they walk up to lead-painted walls and start gnawing on them like they are corncobs.
Lead paint forms toxic dust. The dust gets on floors and into dirt. Children crawl around, and they WILL put their hands in their mouths even if they are "supervised" at all times.
What we are starting to see in presidential debates is an ignorant man talking like he knows everything.
Plenty of old houses in Portland were built in the early 1900s and have lots of lead issues. There have been quite a few uproars over demolitions without abatement of houses with lead paint near schools.
A cheap (very cheap!) device to detect lead in paint. It would have to cost under $50, and better under $30.
If you can detect it you can work on it because you can see the problem.
The only way I know to detect lead with a device (as opposed to chemically) is https://en.wikipedia.org/wiki/X-ray_fluorescence
So, how to make a cheap enough device? You don't need great accuracy - 20% accuracy is fine for this. You need very high sensitivity in the detector because you don't want to generate a lot of x-ray energy in a device hold for household use.
To be practical the device would have to emit so little energy as to be basically harmless even if used on a person. (Low power, but also short duration.)