Monitoring poisons in the environment — a woolly matter

Significant correlations were found between the amount of copper and lead found in washed wool from sheep and in local streams. Median copper concentration in North Ronaldsay wool was comparatively high despite lower soil concentrations. Shetland sheep appeared to accumulate more lead than Swaledale sheep. Another significant observation related to the sex of the sheep – values for wool concentration of both lead and copper were significantly higher in male sheep, which has been linked to the effect of androgens on metabolism.

Dr Sneddon comments, “Sheep wool evidently has potential as a bio-indicator of naturally occurring heavy metal concentrations in upland areas, which have previously not been assessed in this way”. Future studies are planned to assess how the age of the sheep, and where on the animal the wool is taken from, influence results. Furthermore, it is intended to use samples provided by the British Wool Marketing Board in order to provide regional and national focus to this work. In addition, it is hoped that sheep can be of future use in bio-remediation studies on brownfield sites.

Experimental method: A handful of wool was taken from shoulder area of rare and heritage breeds of sheep grazing on hills in the Lake District and North Wales. The wool was then washed to ensure that only metabolised deposits of heavy metals were detected, rather than anything that had stuck to the outside of the wool. Copper and lead concentrations were then determined using highly sensitive equipment which can accurately detect very small quantities of heavy metals. This was compared with data from local streams for accuracy.