Re the Greenpeace "analysis of the analysis",
IIRC a footnote pointed out that the silicon dioxide was "present as complex calcium and sodium aluminium silicates". The former of those is - roughly speaking - clay. My garden is full of it. Round here they dig it up and make it into bricks and tiles. Others turn it into useful items like (serially reusable) plates bowls and cups. Good Greenpeace-lovable stuff in fact. Okay, dried powdered clay is harmful to the lungs in a working or living environment, but only at well-detectable concentrations and over extended periods. Silica it ain't and silicosis it does not cause.
Nil points for the Greenpeace and nil points for the BBC. I am usually sympathetic to the general direction of Greenpeace, but much like my children they piss me off when they do really stupid things. Like that table.
As for neutralisation, there are several options around - what about flue gas desulfurisation? A very long way from being simple, but a local source.
And I am surprised at there being only one person who has asked about the earth dam failure; it looks very like the same mode as the levee failure in New Orleans during Katrina, and that same failure is just waiting to happen in places on the Thames, downstream of the barrier.
Lead in glass? Glass is very stable physically; bury a piece in the ground and it will look identical if you dig it up in 100 years. The aforesaid garden has yielded pieces of glass which seen to be that sort of age (fragments of Cod's bottles, instance). And BTW once-useful pieces of baked clay turn up as well, some datable by their design to ~150 years old.
The chemical stability of glass is another matter - not my field but leaching of lead from old lead glass sounds eminently probable to me.
Mine's the one with the Chemistry degree certificate in the pocket.