Petition for Lead.

Lead is, as probably everybody knows, a toxic metal - so it's not an utterly good idea to use it where it's not absolutely necessary. 

It was, however, widely used in a lot of places throughout history, because it's not only toxic, it's also very useful for a lot of things. Lead is soft and malleable, it can stand a lot of stress before breaking (it stretches instead), it makes a nice white (lead white), and it has a very low melting point - all things that led to lead being used for projectiles, water pipes, roofing, ceramic glazes, lead crystal, stained glass windows, and a plethora of other stuff (fuel additive, if you're looking for a rather modern example...).

Today, there's good replacements for lead about everywhere. However, in some instances in conservation and restoration, lead can still be a critical element, without a good replacement. Sometimes matching the original materials is crucial to prevent unwanted reactions between the original and the reconstructed parts. 

However, due to the toxicity, there's the plan to ban lead completely from being used, in all of Europe. This has been petitioned against by conservators. One of the issues is the primary ban of lead, the second issue is the very hard limits on lead "pollution" in the workspace. The petition, which is supported by German conservators, is currently running and on the EU portal. You can support it by signing it (that will require you to register, for free, on the portal) - and I'd be delighted if you would do so, and spread the word to other people too!

The petition on the EU portal can be found here, under 0724/2023. You can read more about the petition in German on the page of the Verband deutscher Restauratoren.