§ The Countess of Marasked Her Majesty's Government:
Whether they accept that the value of an epidemiological study into the health effects of long-term, low-level exposure to organophosphates in sheep dippers is severely limited unless a dose effect can be shown, and whether they also accept that it is effectively impossible to establish accurately levels of exposure to organophosphates in humans in order for such a relationship to be examined.
Lord LucasTo know the dose-response relation is a great help in the control of any toxic substance. The usefulness of epidemiological information is greatly increased if it can be used to establish one.
The Government do not accept that it is impossible to establish exposure levels for organophosphates. The take-up of organophosphates by the human body immediately following exposure can be assessed by measuring the effects on relevant biochemical processes. Moreover, a key objective of the major new epidemiological study on organophosphate sheep dipping, which the Government announced on 26 October will be to develop a method for estimating exposure directly from the characteristics of the dipping operation. The final results of the study should enable a dose-response relation to be constructed. In particular, they should reveal whether any such relation is one which all exposed people show some effects, increasing progressively with dose, one in which a small proportion of the population is highly sensitive to small exposures 135WA and the rest relatively unaffected; or takes some other intermediate or quite different form.
Even if it proves difficult to develop a method for estimating exposure accurately, the study is designed still to yield valuable information. It will still establish whether there is a causal link between low level exposure to organophosphate sheep dip, even if unquantified, and the neurological indicators being measured. It will also usually examine what such neurological effects mean in terms of actual ill-health.