m-m sex is still disqualifying even if all parties are completely clean and safe. it's discriminatory.

> But why would you care about someone's sexual behavior? The blood must be tested for common drugs and common blood borne diseases regardless, and it's perfectly possible to engage in sexually risky behaviors and not have any venereal disease

Men who have sex with men are something like 50-100x more likely than the general population to acquire HIV. HIV tests do not have a 0% false positive. They will not catch all very recent infections. The rationale for excluding them until recently is that it’s defense in depth and it doesn’t hurt the blood supply much because they only make up about 2-3% of the population.

The current rule is that MSM don’t face a blanket ban, but if you’ve had anal sex in the last 3 months you have to wait because anal sex is inherently more likely to transmit HIV and the tests may not catch a very new infection. Other diseases like Hepatitis have a similar issue.

The answer to all of that is mainly hepatitis C, that can have a window detection of 6 months, even more.

And yes, you can be very careful and get a disease. But they are playing statistics here: over 60% of injected drug users have Hep-C, that means a lot of prostitutes. They won't and shouldn't trust anyone who say "hey, I had unsafe sex against all advice, but was very careful with the tattoo in a dark cellar and the heroin party, pinky promise".

For tattoos, if the artist isn't using a brand new set of needles for you, you risk bloodborne disease transmission, with hepatitis B being a particular danger.

Unfortunately tests are not 100% accurate and there's a window between when the pathogen is present and when it's detectible. Add in that many viruses aren't directly detectable, the tests look for antibodies to the virus.

This is why they usually ask if you've had a new sexual partner in the past 3 or 4 months. This is the window period for detecting some STDs and other diseases.

The UK also has a wait time for many countries including Mexico.

https://my.blood.co.uk/eligibility/travel/article?id=47&titl...

Granted it’s shorter, but there are longer wait periods depending on the country. It’s defense in depth because false negatives happen and some viruses take time to show up on tests.

Blood is tested for disease, but the false negative rate for each test is its own risk.

If you got blood from an addict living on the street engaging in prostitution and tested it, would you trust that blood?

I wouldn't.

The UK had mad cow eons ago, and that's still a risk factor for giving blood in some places.

Sounds like something you should test rather that just rely on heuristics

We do test the blood, but they also do coarse grained screenings like this to avoid some level of waste on intake.

We do test the blood, but they also do coarse grained screenings like this to avoid some level of waste on intake. It's like having client and server side validation.

We do, they are just not cheap enough to do on individual donations so you have to throw away a big batch every time they catch something.

I understand where you're coming from. But on the off chance something unrelated were to go wrong with the blood down the line, it could be shown that a false answer was knowingly given. You have to weigh this risk against keeping "the privilege to give blood". I guess it depends on your values and risk tolerance.

What makes PFAS so difficult to deal with is the fact that they are particularly inert. Teflon works because it doesn't react with almost anything. I've seen some studies about using UV light to kill off PFAS, but that's not going to be desirable when you want those red blood cells to also survive.