With all due respect I'm going to have to ask you post some credible sources to back up your statement above. One person a few years ago puts up a review, very biased, non-scientific, no actual studies, just a lot of opinion masquerading as facts. Since then 1,4 BDO has been so unfairly judged and the same wrong "facts" have been repeated since over and over until the lie becomes accepted truth.
The studies show overwhelmingly over and over that 1,4BDO is almost identical to GHB in safety. 1,4BDO is almost 100% converted to GHB in everyone, takes longer in some than others, but it still is the same in the end for everyone. The extra side effects you might be referring to and not everyone experiences this are all related to the conversion in the liver with the same 2 enzyme process that breaks alcohol down. Depending on a persons level of those 2 enzymes before hand, many never experience anything disimlar to GHB itself. If have low levels of those enzymes it will take longer and more passes thru liver to convert all of it to GHB. This is where you will see the sideeffects of dizziness, nausea, etc. The extra strain on the liver that this process produces is negligble if you drink any amount of alcohol regularly to semi reguluary.
That may be enough to turn some off of being able to enjoy 1,4 bdo, but lets stop with the unsubstantiated "toxicity" smears. I'll wait to start posting studies to let anyone else find them for themselves.
Also 1,4 converts to GHB not GBL. And GBL is the most toxic of the 3, based on 40 years of studies. Its only use is to convert before using into GHB.