Today, quite practical, there is a full movement already ongoing. For recyclers, in the US, its dominated by both coasts, and the key has been the price of gold and other metals, as it rose, so did its increasing practicality.
From a design perspective, the act of making components, designing a PCB, then assembly does generate a lot of chemical byproducts. The key 'R's of waste management remains:
reduce
reuse
recycle
Don't buy more than you need, or throw away what still can be used. From a design perspective, design with as little parts as possible, don't rube goldberg your designs.
Alas, many projects by hobbyists are fun but will be mediocre at best, or useless at worst, so if you really want to build a good item say a PSU, you should buy and mod it, don't build it from scratch, its more eco-friendly because a well designed commercial product could already have parts and design optimized.
For students or hobbyists learning how to build different circuits, don't build it for permanence if cheaper and often better versions are commercially available, build to learn then disassemble and reuse the parts.
For pro designs, I'm designers are aware of the cost benefits of using SMT and PCBs proportionate to the volume of product made, as well as the trade off of building without a PCB and using larger components [ up to through hole] , or dead bug assembly, for low volume items.
For truly obsolete items, can it be reused? For our perspective maybe in terms of parts [ I mean how much can you reuse a 300 baud modem?] : LEDs, wires, connectors, chips, components. Finally recycle the remains properly.
Cellphones are a high turnover item, as was PCs yesterday. That is the trend in design [ you see it in compact digital cameras, kindles, iPads and laptops too], very little in it can be reused once obsolete as to achieve its sizing and efficiency, the human UI and electronics are all highly integrated. Since the casing & switches wear after use, once deteriorated, the electronics are difficult to reuse as the design is tightly bound to the UI. Likewise, devices that use FPGA, ASIC, uC etc., are very customized to support the programmed chip; its rare to reuse these chips or support electronics, so in the end the solution is recycling.
The question is, how practical it is to create products that not only aids recycling but also alleviates recyclers from using hazardous methods to process them? Or perhaps the solution is to set up safer recycling infrastructure in these countries?