In 2013 in Minamata, Japan a convention was held which led to an agreement to which most advanced countries signed up committing them to using less mercury and thereby reducing the risks of mercury to the environment.
All sources of mercury were targeted for reduction including LED light bulbs, fluorescent tubes, vaccines, fertilisers, thermometers and batteries.
Dental amalgam filling uses mercury and so are included in reduction targets.
In the UK to meet these targets we are now not using mercury based amalgam fillings on pregnant women and children under 15 years of age.
Amalgam has been a tried and tested material in dentistry for 125 years and will still be used and continues to be safe to use but will eventually be phased out as suitable alternatives which are cost effective become available.
As for changing old amalgam fillings for more glamorous white ones, my advice is if they are working and not obviously visible then leave them alone until they need replacing.