Environmentally sustainable electronics
You may want to look at recommendations from the circular economy ... perhaps starting at the Ellen Macarthur Foundation
The underlying idea is design with a view to repair, recycle and re-use. Arcatus' answer hits one key point ... reliability reduces the volume of junk to be recycled.
But there are two aspects to reliability ... avoiding failures is only one, but the easiest for the designer alone.
Ease and speed of repair is another, which requires a systemic approach different from some modern companies. There's no point making a subassembly replaceable if it's inside a case that's glued or welded shut. And there's no point if the company has no spares supply chain or no commitment to keep spares available beyond the guarantee lifetime. I touched on this in another Q&amp;A.
To illustrate the systemic approach : I replaced my car a couple of years ago; the roof bars are adapted to each car model with a relatively cheap and simple fitting kit. Great design! However when the manufacturer introduced a new system, they immediately obsoleted the fitting kits for the older system. So, not like that...
In the kitchen, I found I can cheaply and easily replace the controls and heating elements on a 30 year old stove. A $10-$20 part, a few screws, spade clip connectors, job done. Microwaves, not so much.
Going back to Arcturus' answer; he deprecates electrolytic capacitors, with good reason. But if you can't eliminate them, consider moving them along with all the hot power supply components to a second cheap PCB, replacable separately from the main unit. (You have to factor in the reliability of connectors though; it's not an open/shut decision).
Or farm the lot out to an external PSU, like a laptop brick or USB phone charger. It's ideal since it's easily accessible, replacable, and pretty standard.
Design either for zero failure rate, or easy access, easy repair, and good spares availability (where possible, using standard or very common parts).
Another example : this laptop (after seven years) has a new power supply, a new (and greatly improved) disk, and new and bigger memory. Maybe I'll get another seven years out of it... The case was designed with 3 screws and subtle disassembly hints moulded into the underside, making it a dream to work on compared with some.
There is room to be imaginative : for example, while you can't realistically 3D print components for a production run, you might consider open sourcing a design at the end of its maintenance lifetime so that 3rd party spares can be produced. (This is being done for at least one model of pre-WW2 lathe!) A systemic approach might put together a suitable archive at design time, for public release after production ends, to allow lifetime maintenance. (Of course it may not cover everything, for IP protection purposes)
I don't know of ISO standards for these ... yet ... they may emerge from the aforementioned circular economy project.