I don't think "US and Canada do it" is a very effective argument for something being safe or reasonable. The reality is - We don't know what the effects are, and we can't even be completely sure they're doing what they say they are in the first place. The radioactivity may be low, but the presence of manmade tritium may well cause issues we don't even realise, and as always we're playing a gamble that "this number low so it's probably safe maybe". And that is undeniably a gamble, even if a low-risk one.