>At least here in the US, it seems many people believe that if it's available for sale, that means a government agency deemed it safe, neglecting to consider that what a government agency declares safe may not actually be safe. This happens routinely for a variety of reasons - corporate capture (big business teaming up with big government to screw over human beings), gross incompetence of government employees (who in turn, are nearly impossible to fire, even with cause), complex modes of unsafety (per- and poly-fluorinated substances are bioaccumulative and persistent, and the relationship they have with our health remains ambiguous), complete lack of awareness of the risk (in the last week or so, we just discovered chloronitramide anion exists in the water supply of about 1/3 of the USA, little is known about the health effects it has on mammals in general, let alone humans), etc.

That's not actually how it works in the US. The standard is "Generally Recognized as Safe" (GRAS)[0], which requires the manufacturer to "confirm" that an additive is "safe."

At least that's been the requirement since 1958, although some 700 existing additives were declared exempt from the potentially biased/unconfirmed testing of the manufacturer.

If, as you suggest, "...many people believe that if it's available for sale, that means a government agency deemed it safe", those folks are woefully misinformed.

[0] https://en.wikipedia.org/wiki/Generally_recognized_as_safe