How do chemists find out whether or not a chemical is toxic without, well, ingesting it?


How do chemists find out whether or not a chemical is toxic without, well, ingesting it?

In: Chemistry

I understand saccharin was discovered only because a chemist by the name of Constatin Fahlberg happen to notice a sweet taste on his fingers after a day in the lab working with new compounds.

That said, to answer your question, if you know a certain series of unstable nitrogen compounds like nitroglycerin is toxic, you can safely deduce that if you were to create another in that same series, it would be equally toxic.

My guess is, a good many compounds are just indicated as toxic, because it’s a reasonable conclusion, and not because someone tasted it to be sure.

Ok, chemists are told not to lick the science. So they suggest others don’t either.

In all actuality, lab testing routinely involves animals and since our closest relatives besides monkeys are mice, if a mouse ingests it and they die it is likely to hurt humans too.

ETA: yes, I am a sci dork who forgot to mention why we use the mice/rats outside of similar digestion. 😣

Scientist pretty much determine if a chemical is toxic by taking a reference group of animals and check at which dosis kills half of the population. The measurement is called Ld50 (lethal dosis, 50%). By taking the biomass of mice for example into account a lethal dosis for humans can be determined. This is not always reliable due to physiological difference between the two, so sometimes they check the dosis on human tissue cultured in the lab.

All chemicals are toxin when breaking a certain threshold.

There’s primarily 2 methods: **In Vivo** (Animal or human testing) and **In Vitro** (test tube cultures).

>In vitro toxicity testing is the scientific analysis of the effects of toxic chemical substances on cultured bacteria or mammalian cells. In vitro (literally ‘in glass’) testing methods are employed primarily to identify potentially hazardous chemicals and/or to confirm the lack of certain toxic properties in the early stages of the development of potentially useful new substances such as therapeutic drugs, agricultural chemicals and food additive

So ELI5: stick some cells under the microscope, introduce potential toxin and observe.

In Vitro observes only the particular cells or bacteria that you have selected and is not able to make full analysis of additional factors like immune response. Due to its limitation of the cultures not being part of an intact organism In Vitro is normally used as the first step and doesn’t eliminate to need for In Vivo (Animal or human testing).

They dont. Like Albert Hofmann who found out how to make acid or LSD. He thought well surely 250 microgram wont have any effect on humans. So he ate 250 micrograms and low and behold 250 microgram is enough for a really good intoxication.

Question is LSD toxic?

According to this definition it is

>”What makes a chemical toxic? The toxicity of a substance is its ability to cause harmful effects. These effects can strike a single cell, a group of cells, an organ system, or the entire body. A toxic effect may be visible damage, or a decrease in performance or function measurable only by a test”

And yes LSD will make you perform suboptimally on tests.

There are multiple methods. The easiest is to test it on other mammals. If we want to reduce testing we have other methods. We can test it on human or animal cells in a petri dish. We can compare chemically similar substances that were tested in the past and draw conclusions from that. Building on that we may notice trends, for example generally the more aromatic rings a compound has the more carcinogenic it is. there are accepted software models that can predict the toxicity if a chemical is within a certain family of compounds. Finally if there have been any accidental releases we can get data from that.