URL: http://216.31.193.173/ewsoe/english/4_4.htm

   

<h>4.4 Health of the environment

   

<h>Eutrophication

<p>Concentrations in Welsh rivers of the main plant nutrients (phosphate
   and nitrate) are generally much lower than those found in the midlands
   and south-east England. There are correspondingly fewer perceived
   problems associated with eutrophication compared with lowland England.
   However, nutrient enrichment arising from sewage inputs and
   agriculture does cause water quality problems in all types of aquatic
   environment, affecting drinking water supplies, conservation interests
   and recreational uses.

<p>A number of water-supply reservoirs are regularly affected by
   blue-green algal blooms notably Llandegfedd, Wentwood, Cefni and
   Nant-y-Frith, with implications for water treatment and supply.
   Conservation interests are being affected at a number of important
   wetland sites on Anglesey, at Bosherston Lakes in south Pembrokeshire
   and at Llangorse Lake near Brecon. Eutrophication is affecting the
   survival of two endangered fish species: the gwyniad in Llyn Tegid and
   the arctic charr in Llyn Padarn. Blooms of blue-green algae can
   interfere with recreational activities at a number of waters,
   including Llysyfran Reservoir and Eglwys Nunydd. Despite the
   environmental safeguards to deal with the consequences of
   eutrophication specified in the Cardiff Bay Barrage Act, algal blooms
   are likely to affect recreational uses and aesthetic enjoyment within
   the impoundment.

<p>The Wye below Hereford and the 
   Loughor below Garnswllt STW have been designated as sensitive areas
   under the Urban Waste Water Treatment Directive. In both stretches,
   phosphate inputs from sewage works have been shown to promote plant
   growth which may cause serious de-oxygenation during the night under
   conditions of high temperature and low river flow. Resulting low
   concentrations of dissolved oxygen have been implicated in fish
   mortalities on the lower Loughor in 1984, 1990 and 1995. Besides these
   designations, there are many smaller watercourses in lowland areas
   which are affected by growths of algae. These effects appear to be
   chiefly related to inputs of nutrients from agricultural sources and
   may reduce the survival of salmonid eggs and fry in heavily affected
   stretches.

<p>In general, scientific understanding of the links between nutrient
   inputs and eutrophication in estuarine and coastal waters is much less
   advanced than for freshwaters. Nevertheless, eutrophication appears to
   be connected with periodic low concentrations of dissolved oxygen in
   the Loughor and Dee estuaries. The impoundment created by the Tawe
   Barrage in Swansea is subject to blooms of marine algae, and the
   impoundment has already been designated as a sensitive area.

<p>Historical records
   indicate that algal blooms in coastal waters have been a periodic
   natural occurrence. However, the concentration of blooms of
   Phaeocystis between Liverpool Bay and the Menai Strait in north Wales,
   around Aberystwyth and in Carmarthen Bay suggest an influence of
   enhanced nutrient inputs in these areas arising from sewage,
   agricultural run-off and industrial discharges. Concentrations of
   nutrients and algae in the Irish Sea have risen steadily since the
   1960s, so this problem appears to be increasing. Foams and scums
   arising from blooms are aesthetically unpleasant, can be mistaken for
   sewage and give rise to numerous public complaints over bathing water
   quality.

<p>Blooms of toxic marine algae are relatively rare around the Welsh
   coast although blooms of the dinoflagellate Gyrodinium aureolum have
   been linked to fish and shellfish mortalities in Swansea Bay in 1989
   and St. Brides Bay, Pembrokeshire in 1994. Other blooms of potentially
   toxic alga include the dinoflagellate Alexandrium tamarense which has
   been recorded in the upper part of Milford Haven since 1995, and a
   bloom of Dinophysis was recorded within the Tawe impoundment in 1995.
   The former can produce Paralytic Shellfish Poisoning and the latter
   Diarrhetic Shellfish Poisoning, but no effects on human health have
   been observed to date.

<h>Synthetic chemicals

<p>The distribution of individual synthetic chemicals in the Welsh
   environment reflects their physical and chemical properties, and the
   way in which they are dispersed. The persistent substances are poorly
   soluble in water but soluble in fat. They therefore attach to sediment
   particles, accumulate in the fatty tissues of animals, and pose the
   greatest risk to animals at the top of food chains. In freshwater
   these are fish-or insect-eating aquatic birds and aquatic mammals,
   such as otters, and in the marine environment seals, porpoises,
   dolphins and seabirds are at greatest risk. Clearly humans are also at
   potential risk from the consumption of contaminated wild animals. The
   techniques for monitoring distribution and measuring the effect of
   these chemicals are difficult and expensive. Consequently only the
   apparent high priority chemicals have received attention so far, and
   techniques are still being developed for many groups of synthetic
   pollutants.

<h>PCBs

<p>PCBs have been found to be present in freshwater eel tissue at sites
   throughout Wales, but highest concentrations were found in the lower
   reaches of industrialised catchments in the south-east and north.
   Aerial inputs derived from global sources may also be a significant
   route for PCBs found in dipper eggs (an insectiverous riverine bird)
   at remote rural sites.

<p>In the marine environment, contamination is related to past industrial
   production, use, disposal and subsequent transport with fine sediment.
   Marine sediments areheavily contaminated close to river mouths and
   docks in the Severn Estuary/Bristol channel, contaminated at offshore
   sites in the Severn Estuary and Swansea Bay, and slightly contaminated
   in the centre of the Bristol Channel. Although fish from Cardigan
   Bay and the Severn Estuary do not appear to be seriously contaminated,
   high concentrations have been found in marine mammals from these
   locations. This appears to be evidence of high accumulation in
   predators at a considerable distance from PCB sources.

<h>Dioxins

<p>The greatest risk of contamination by dioxins/furans is near potential
   sources such as waste incinerators. The Welsh Office commissioned a
   study of dioxins/furans and PCBs in the environment around the
   high-temperature incineration plant of Rechem at Pontypool in 1991.
   With the exception of a localised area within 500m of the plant,
   measured concentrations of PCBs and dioxins/furans in the environment
   provided little evidence of levels of contamination any different from
   those encountered in similar areas elsewhere in the UK. The effects of
   this plant should not give rise to undue concern, according to
   accepted criteria and guidance on health effects for these compounds.

<h>Pesticides

<p>Organochlorine pesticides were used for a wide range of applications
   in Wales, sheep dipping and wool preparation being the main rural use.
   Use of dieldrin and DDT in the UK was banned in the late 1980s, but
   significant residues of these pesticides remain in eels from
   agriculture-intensive and industrialised catchments. In the marine
   environment they are still found in the fatty tissues of marine
   mammals, and an inshore Cardigan Bay sediment sample contained the
   highest level of dieldrin contamination of all sites in a national
   survey. Pentachlorophenol was synthesised in Wales and is still
   found in the discharge from the manufacturing site, although
   production ceased many years ago. Residues remain in sediments
   surrounding the discharge, and a slight effect on the invertebrate
   community there is evident. The biological impacts of organophosphate
   and synthetic pyrethroids are covered in Section 4.2.

<h>PAHs

<p>Polycyclic aromatic hydrocarbons (PAHs) that result from combustion of
   fossil fuels and waste material are found widely in industrialised
   areas, in road run-off and in marine sediments close to shorelines.
   Many are moderately persistent in the environment, but are broken down
   in fish and higher vertebrate animals. They can cause the same sorts
   of cellular effects as PCBs and dioxins.

<h>Organotin

<p>Use of tributyltin (TBT) antifouling paint on boats less than 25m in
   length ceased in 1987, and the application and removal of such paints
   on boats of 25m or more became subject to regulation in 1996. Evidence
   of impact on the affected species (dog whelk) is limited to parts of
   Milford Haven and Holyhead harbour, close to current sources of TBT on
   large vessels. Organotin compounds have been used in other
   applications and their well-documented endocrine disruptive effect may
   require further assessment.

<h>Radioactivity

<p>Surveys in Wales show that the average radon concentration in Welsh
   homes is 20 becquerels/cubic metre, equivalent to about half of the
   total radioactive dose received by the population. Radon levels are
   higher than this average in parts of Glamorgan, Pembrokeshire,
   Radnorshire, Anglesey and north-east Wales due to the underlying
   geology. More extensive areas with high radon concentrations occur
   elsewhere in the UK such as Cornwall and parts of north-east Scotland.
   Raised levels of radon gas increase the risks of lung cancer and the
   National Radiological Protection Board (NRPB) has advised that indoor
   radon above an Action Level of 200 bequerels/cubic metre should be
   reduced. It has been estimated that Wales has about 10,000 homes with
   radon levels above this level.

<p>In June 1998, the Welsh Office announced a targeted testing programme
   for four areas at the highest risk from radon gas emitted by natural
   sources. Householders in these areas can receive detectors from the
   NRPB to monitor radon gas in their properties over a three-month
   period. The need for measures to reduce levels will then be evaluated.
   Grants to assist in this work may be available from local authorities.
   New homes are protected through the building requirements in
   high-radon areas.

<p>The results of extensive monitoring of the effects of nuclear
   facilities on levels of radiation in the environment are reported
   annually by MAFF. This includes an assessment of the maximum exposure
   to radiation to humans from each source. For terrestrial sources,
   these assessments are generally based on concentrations in
   agricultural produce local to the nuclear facility. For aquatic
   foodstuffs, the assessment is based on concentrations in species
   commonly harvested for human consumption. The calculation of the dose
   received is based on consumers with the highest potential intake of
   the food in question. The exposure from each of the nuclear
   facilities in Wales was a small percentage of the maximum limit (1
   millisievert) for members of the public from artificial sources of
   radiation .

<p>Monitoring in 1998 of the impact of the discharges from Amersham in
   Cardiff established that there were relatively high concentrations of
   tritium in flounders (up to 50,000 bequerels/kilogram) caught near the
   effluent discharge from the plant and also in sediments within the
   Severn Estuary. Previously it had been assumed, in accordance with
   other studies, that concentrations in fish would be similar to that of
   ambient seawater. The finding that tritium could be bioaccumulated
   required a reassessment of the radiation dose to the critical group of
   fish consumers in Cardiff, and the 1997 figure of 3% has been revised
   to 6%. This is still a small proportion of the dose limit but
   nevertheless the unexpected bioaccumulation of tritium was of concern
   and resulted in a requirement for tritium discharges to be reduced
   significantly .

<p>A survey was undertaken in 1997 to determine the concentration of
   technetium-99 in selected animals and plants around the Welsh coast.
   Highest concentrations (1836 bequerels/kilogram) were found in brown
   seaweed at sites closest to the Sellafield discharge along the north
   Wales coast. Concentrations decreased southwards with lowest amounts
   present at sites in the Bristol Channel.

<p>The highest concentration found in periwinkles in the same survey was
   152 bequerels/kilogram. This is not a high concentration in relation
   to the risk to human health since consumption of 12 kilograms would
   result in a radiation dose of 1 microsievert, which is only 0.1% of
   the dose limit.

<h>Acid rain

<p>Nitrogen now contributes 60% and sulphur 40%
   of the total acidifying input from atmospheric deposition in the UK.
   Some 40% of nitrogen deposition is oxidised nitrogen from the
   combustion of fossil fuels, while 60% takes the form of ammonia,
   mainly from agricultural sources within the country. Impacts by
   acidification from nitrogen and sulphur emissions can be assessed by
   the critical loads approach, which shows where deposition rates of
   atmospheric pollution are high enough to cause environmental harm.
   This demonstrates that acidity critical loads for soils and freshwater
   systems are widely exceeded by the combination of nitrogen and sulphur
   deposition,.

<p>Cuts in sulphur emissions have reduced deposition in upland Wales from
   3050 kg/ha/year in 1984 to 2030 kg/ha/year in 1995. Cuts in emissions
   of oxidised nitrogen have also contributed to reducing the affected
   area, but substantial further progress is needed. The effects of
   reductions to date are apparent in declining sulphate concentrations
   and slight reductions in the acidity of 77 streams surveyed in 1984
   and 1995. However, these improvements have not yet led to biological
   recovery .

   