I'm afraid that we've brought this down on ourselves. There has been the ban on shooting duck with lead in England for 15 years or so. The report cited by the BBC describes how >75% of duck sold as shot in England had been shot with lead, rather than steel etc. (I have to admit that I can't find a reference to this figure - the one that I am aware of is 69% from a study published in 2010, but in either case, it is a lot of ducks). That means that this law is being broken and broken on a pretty major scale. I don't dispute this - I've seen plenty of inland duck drives where no-one bothers to swap cartridges.
The RSPB/WWT etc are getting involved because there are still lead pellets being shot into areas where waterfowl live, and they are ingesting them as 'grit' and consequently absorbing high levels of lead into their bodies. This can (but does not always) kill the ducks, and a single pellet ingested leads to a 12x rise of circulating lead levels (Mautino & Bell 1986). It's not even affecting ALL waterfowl - wigeon seems to be completely free of ingested lead. To a large extent, RSPB/WWT would not have been too worried about effects of shot game on human health - it's not their remit, and terrestrial birds do not ingest lead/gravel to nearly the same extent as waterfowl, so the effects of residual shot outside of wetlands on birds is negligible. It's the fact that shooting is incidentally responsible for putting toxins in the food chain of wild waterfowl that has provoked this report and the involvement of the various biologists.
If there had been good compliance with the original ban on shooting duck with lead then we could have made a coherent argument that original spent shot is slowly sinking, none more is being added, risks are decreasing etc. As it is, the report can be used to project shooters as lawbreaking, inconsiderate, nature hating, not to be trusted, unable to police themselves etc etc. The inevitable conclusion is that if shooters cannot restrict themselves to not using lead shot when shooting particular game, then the simplest solution is to ban all lead shot.
If the argument had simply been about lead in shot pheasants etc and the attendant risks to human health, then it could have been rebuffed either by explaining that we can be careful when preparing/eating food, or framing it as one of the many food choices that we make - how much alcohol to drink/red meat to eat/bacon to fry, offsetting risks with benefits including pleasure. We could even have legitimately demanded a discussion on bird welfare casting doubts on the efficacy of steel shot in humane killing. As it is, it's become one of bird conservation, biodiversity and criminality, which are much harder to counter in any rational way.
I don't dispute that some people want to see shooting banned or heavily restricted come what may (Avery waddles into my mind) and are using the lead ammunition to fuel their broader campaigns. By a refusal to comply with the original resolution, banning lead shot for duck, we've made their task easier. I'm afraid that by burying our heads in the sand, as seems to be the case on this and other similar threads, we're also digging our own grave.
Mautino, M., & Bell, J. U. (1986). Experimental lead toxicity in the ring-necked duck. Environmental research, 41(2), 538-545