Assuming agencies only have advisory capabilities and that regulation itself is handled by lawmakers directly. The determination of what is safe or not becomes a matter of who has the best lobbyists; any actual damages will occur years down the line, will be visible only in statistical terms (i.e. a higher rate of leukemia), and will only affect people without significant political power. This is a textbook description of an issue which democratic institutions are spectacularly bad at handling: expert knowledge is required to understand the issue, there is no immediacy, and the consequences are delayed while the costs are up-front. Consider climate change---it will cost a shit-ton of money, cause a crap-load of damage, and yet humanity has collectively done essentially nothing to prevent it in something like 40 years.

Now, it's possible that legislative regulation could work, if the legislators essentially rubber-stamp the advisories from the agency, but still allows political influence in the issues. Consider PVC and cigarettes.

The approach, then, is for the legislature to delegate authority for regulation, within specific parameters, to an executive agency. The agency then sets the regulations, which the legislature can override with exactly the same ease as they would regulate them in the parent's model.

I am unaware of any country that relies on legislative regulation and is regarded in any sense as successful. In fact, political interference in regulations is almost universally regarded as a bad thing.

Anybody have a specific example of regulatory excesses?

[At one point I got trapped in a conversation with a cousin's husband, who had recently gotten fined by OSHA or the state equivalent because he had diesel stored in the correctly color-coded container, but it did not have "diesel" written on it. I thought about mentioning people who didn't know the color codes (Red = gasoline, yellow = diesel, blue = kerosene, and green = oils) or about the color-blind, but I prefer to avoid arguments.]