Royal Commission on Environmental Pollution

Thank you for your consultation letter of 19th October 2000 inviting views on key issues in relation to the above study. Scottish Natural Heritage (SNH) was established under the Natural Heritage (Scotland) Act 1991 to secure the conservation and enhancement of the natural heritage of Scotland. SNH is, therefore, replying with regard to the known and suspected effects of such chemicals on habitats and species within Scotland. SNH is making little comment on the details of assessment and regulatory systems. However, English Nature, which acts as a Lead Agency on behalf of the Countryside Council for Wales, the Joint Nature Conservation Committee and SNH, on certain pollution issues, will be adding more detail on the assessment and regulatory systems.

An overview of existing scientific knowledge on the long-term effects of chemicals in the environment might consider categorising such chemicals as

· those that persist either in the environment or within the organism,
· those that have diffuse and/or diverse effects across ecosystems,
· those with a short persistence in the environment but a localised impact, and
· those that have endocrine disrupting capabilities.

1.   Chemicals that persist either in the environment or within the organism
Chemicals that persist in the environment, that may have long-term effects on ecosystems due to continual exposure, include persistent organic chemicals such as polychlorinated biphenols (PCBs), polycyclic aromatic hydrocarbons (PAHs), polycyclic biphenol di-ethers (PBDEs) and dioxins. They may have both direct and indirect effects. For example, the earlier organochlorine insecticides killed insects, the food of insectivorous birds, but also less directly had effects on the shell thickness of peregrine falcon eggs, leading to a reduced breeding success in this bird species.

This example demonstrates that persistent residues of herbicides and pesticides are known to accumulate through the food chain. Of particular importance is the effect of the so-called 'second generation' rodenticides on birds of prey, such as barn owls, red kites and buzzards. We do not yet know whether there are other secondary indirect effects on the species, and communities, in the British countryside, such as red squirrels picking up the baits placed outside. Determining whether there are such knock-on effects on species' populations and/or community characteristics also needs addressing.

2.   Chemicals that have diffuse and/or diverse effects across ecosystems
Chemicals under this heading can be divided into two types - those that are deposited from the atmosphere and the heavy metals - although this classification is not totally mutually exclusive.

Chemicals that are deposited from the atmosphere include those that have eutrophying and acidifying effects (i.e. NOx and SOx). Although sulphur deposition is declining, nitrogen oxides deposition is becoming a major contributor to the acidification of ecosystems. However, the underpinning science to quantify the role of nitrogen is weaker than that for sulphur. It is possible that large areas of semi-natural vegetation in Scotland are subject to nitrogen deposition in excess of critical loads for such ecosystems. As far as SNH is aware, there are no current protocols that would act to reduce these levels in the coming decade, nor has much attention been paid to synergistic effects between acidification and eutrophication upon species and ecosystems.

Whilst there are some studies on eutrophying and acidifying effects on habitats and species, there has been little assessment made of the effects of ozone on non-crop plants. Ozone concentrations within the uplands of Scotland are expected to increase. No-one has yet defined what this means for upland ecosystems. However, it is possible that concentrations of ozone represent the greatest direct gaseous pollution threat to vegetation in Scotland.

Heavy metal contamination in Scotland can be considered from two points of view. First, there is some concern that mercury and cadmium contamination from incinerator waste can have both acute and chronic effects on birds. Second, contamination of peatlands close to industrial centres with nickel, copper, lead and other heavy metals has recently been identified. It is not clear what effects these metals are having on peatland ecosystems generally, but it is known that such metals can be released in high concentrations after the peat has had a period of drying out (and hence oxidization) and then experiences heavy rainfall. The high concentrations of released heavy metals are suspected to exceed critical limits locally in river and stream ecosystems. This is of concern because heavier rainfall events following periods of relative dryness (or drought) are becoming more frequent in Scotland with the changing climate. The movement of such metals into freshwater ecosystems therefore needs to be monitored and their effects (both direct and indirect) arising from movement throughout freshwater, riparian and, perhaps, estuarine ecosystems needs to be investigated.

3.   Chemicals with a short persistence in the environment and localised impact
Biocides used as anthelminthics on livestock (e.g. avermectins) persist once excreted and are already known to affect invertebrates such as dung beetles which can, for example, have a knock-on effect on the chough populations. However, it seems that there has been little work on discerning whether there are secondary impacts within the ecosystem. The long-term effects of biocides used against sea lice within salmon farms are presently being addressed by a 3-4 year, £4m, research study funded by MAFF, DETR, the Scottish Executive and SNIFFER. The project will consider effects on benthic and pelagic ecosystems, although bioaccumulation through the food chain (on fish-eating birds and mammals such as otters) will not be considered. However, because bioaccumulation may occur (cf. the 'persistent chemicals' category, 1, above), research in this area could be considered.

Airborne ammonia generally has a localised effect. This may cause a long-term effect at particular locations if the source of ammonia emissions continues, but this needs to be linked to the other N compounds that have an acidifying effect on habitats and species.

4.   Endocrine disrupting substances
It is believed that there are approximately 100,000 man-made chemicals circulating in the environment that may have an endocrine disrupting effect. Many have never been tested for any potential deleterious effects, be they endocrine disruption alone or other adverse effects together with the endocrine disrupting impact. The ecological impact, in terms of effects on population dynamics and species communities, is an area which requires more research. There is evidence that some endocrine disrupting substances are accumulating through the marine and freshwater food-chains. There is therefore a need to clarify whether these effects are being passed on through the natural ecosystems to top predators like otters or fish-eating birds. This could have implications for the type of antifoulant paints approved for use to prevent the colonisation of marine molluscs on boats.

With the use of sewage sludge on forest and agricultural land there is the need to consider the implications of endocrine disrupting substances both on the target land and on nearby ecosystems. We believe that there have been MAFF-funded projects considering the contamination of human food by such substances, but little attention to the effects on wildlife. Whilst SNH believes that there is some monitoring of the content of sewage sludge, it appears that monitoring for endocrine disrupting substances is not covered by the regulations for disposing of sewage sludge to land.

Comments on current assessments and regulatory systems
There are gaps in the types of current assessments made on the use, disposal and movement of chemicals through ecosystem. Current assessments also tend to focus on the direct lethal effects. However, consideration should also be given to sub-lethal impacts on the population dynamics of certain indicator organisms, as well as to the more widespread ecosystem effects. There may be instances where monitoring might need to be expanded across the ecosystem rather than just focusing on one or two populations. In other words, assessments and the regulatory system need to take a more holistic view of the effects of environmental chemicals on ecosystems, including freshwater and marine ecosystems and the soil. Surprisingly little is known about the effects of environmental chemicals on the soil ecosystem, which is important in the decomposition of many organic substances, in the cycling of nutrients, and as a first stage in the hydrological cycle.

If you wish to follow up any of the points raised in this response to your consultation letter, could you please in the first instance contact Professor Michael B Usher, Chief Scientist, Scottish Natural Heritage, 2 Anderson Place, Edinburgh EH6 5NP.

Back to Index of comments to the scoping of the Chemicals Study