Digressing slightly I am sure I saw a program on TV some years ago that parts of the country was sprayed in the 50’s with chemicals as an experiment.

Some of the experiments in the UK and US.

http://www.mod.uk/NR/rdonlyres/70A71F1A-831B-4618-918E-D263384DA684/0/ZincCadmiumSulphideDispersionTrials.pdf

http://books.nap.edu/openbook.php?record_id=5739&page=R1