HAVING been invited to comment on the foregoing letter, I would first say that I am entirely sympathy with its main thesis: a plea for the suppression of dangerous dusts by all known means. Unfortunately the authors' enthusiasm for dust suppression leads them to damage a perfectly sound case by overstatement. They seem, indeed, almost to imply that silicosis can be so completely and satisfactorily prevented by masks and ventilation that the investigation of its cause and cure is superfluous.