Aluminium a Threat to Knowledge?

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Over on the RallyUK forum they are talking about the environment (you have to register to see it, not for profane eyes). There "metal detectorist" Julian Evan Hart warns of a serious problem, caused by the littering of the British countryside by the louts who visit and throw down drink can pull tabs, tinfoil and other such rubbish:

many local historical sites are becoming saturated in aluminium and making it extremely difficult to recover metallic artefacts such as coins and brooches and that side of things whilst not as important as the food we eat or environment we live in.... but like the latter factors will effect our national heritage and academic learning from the past.

Well, of course not as much as a threat if these "coins and brooches and that side of things" are taken away without any record whatsoever being made - Mr Hart Evans distinguished himself on a recent forum (see here) by saying he does not report his finds to the PAS. Also of course it is a rather narrow - antiquitist - view, isn't it, that our "academic learning from the past" ("about", surely) is based entirely on being able to recover "coins and brooches and that side of things" from various bits of the land with metal detectors.

UPDATE 13th July: Mr Hart Evan noted these comments, tells his readers aluminium is toxic in the food chain (it is not, it is a component of clay minerals too) but did not answer the other points.

Vignette: No longer in use in some parts of the world, but you can still find them on cans in Egypt.

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