Pollution in Ireland

Overall, the quality of water in Ireland is still quite good compared to other countries, see the latest reports here. Over the past thirty years, however, water quality has decreased and incidences of pollution have cropped up as follows:

Fish Kills

This refers to a localised dying off of aquatic life that can occur as a result of oxygen depletion in a water course. Other causes include hazardous waste spills, over-population of a particular species or unusual weather conditions. Fish kills in Ireland are commonly caused by untreated sewage, agricultural wastes and industrial effluents. 

In 1996 a large fish kill occurred in the Dodder River in Dublin which was said to be the direct result of industrial waste flowing into the river. In October 2007, Laois County Council were prosecuted by the Southern Regional Fisheries Board following investigations into a fish kill on the Owenass River as a result of discharges from the Council's Sewage Treatment Works at Mountmellick.

Dairygold in East Cork was fined €12,000 and ordered to pay legal costs after it killed 20,000 fish in 2012 by accidentally letting 150 litres of toxic insecticide run into a river. The fish kill took place as grain was being transferred from one Dairygold Agribusiness silo to another at the Mogeely site.

In 2017 a car tyre dumped in a sewer killed hundreds of fish in the river Tolka, multiple incidences of fish killed by agricultural slurry have also been recorded. 

Foreign Species

Non native species of plants or animals represent a huge threat to biodiversity as they can displace other native species and upset the natural balance of an ecosystem. They can also change the food web of a habitat, and spread disease if they are of a parasitic nature. New species are capable of out-competing native species for food and sometimes even diluting their gene pool. 

The zebra mussel (named because of its striped shell) is a foreign species introduced to the Shannon Estuary in the 1990s. It is presumed they attached to marine vessels coming from the Black Sea or the Caspian Sea. They are small shellfish shaped like marine mussels that feed by filtering the surrounding water and removing plankton from it. This process changes nutrient cycles, and filters out phytoplankton that forms the basis of the food chain. Each zebra muscle sieves as much as one litre a day. They can clog pipes and drains causing reduced water delivery to industries, power plants and fish hatcheries.

Cryptosporidium in Galway

In March 2007, parts of County.Galway experienced first hand how water pollution can affect everyday life and people's health. An outbreak of Cryptosporidium, a parasitic organism, occured in Headford, Moycullen and Galway City through contaminated tap water. This parasite multiplies in the gastrointestinal tract of mammals and then is excreted in very large numbers. In this case a spate of stomach illnesses with pains and diarrhoea alerted authorities to the problem.

Lough Corrib was found to be contaminated with the parasitic organism. The main culprit was a water filtration plant in Terryland that uses the water from the lough and supplies 30% of the county's water. Some 90,000 people in Galway were forced to boil or buy water because of the dangers ingesting the contaminated supply and approximately 180 people became ill as a result of the outbreak. These 'boil notices' remained in place for weeks after the event occurred to ensure the safety of public health.

The outbreak was eventually contained by upgrading existing water treatment and filtration systems and also by importing water from the nearby Luimnagh plant at Tuam. This plant has modern facilities which provide for Cryptosporidium eradication and filtration. However, in early 2008 another outbreak occurred, though this time on a minor scale with no health impacts. The organism was identified early enough in the treatment process to warn the public. 

Irish water detected Cryptosporidium in 25 public water supplies in 2018. This shows a significant increase compared to previous years, making it a cause for concern. This was mainly down to inadequate treatment processes or infrastructure, absent treatment processes and operational issues in water supplies (EPA, 2018). For guidelines on when a boil notice is issued in your area see the Irish Water website.

Boil Notices

After the severe flooding throughout the country in late 2009, other water supply contamination scares occurred in Gort, Co.Galway; Carrickmacross, Co.Monaghan; Sligo Town and Co. Limerick .

In the incident in Galway the Health Service Executive (HSE) discovered bacteria in the Gort water supply after a routine inspection, while E.Coli was found in the Monaghan supply. The heavy downpours in August were blamed for bringing contaminants into the local water supplies and some of these areas were issued with 'boil notices' - where householders must boil all water before use - to prevent any adverse health effects occurring.

In May 2013, Roscommon County Council advised consumers in the areas served by the Boyle and Boyle/Ardcarne Regional Water Supply Scheme to boil water before use due to an unidentified cryptosporidium outbreak. Similarly, in May 2015 a boil water notice was issued in Mayo for the Westport Water Supply Scheme.

Following heavy rainfall in November 2019, a boil water notice was  imposed by Irish Water on 600,000 people that resided in North Co. Dublin, Kildare and Meath. Irish Water is unsure when this notice will be lifted due to problems at the Leixlip treatment plant where the quality of the water coming from the plant cannot be guaranteed. High levels of suspended particles, which have exceeded acceptable levels, have been found in the water causing it to appear cloudy. Conditions of the plant have been further exacerbated due to a yellow weather warning which was issued by Met Eireann for that specific region. With further heavy downpours and spot flooding events continuing, there is no guarantee of when affected homes and businesses will  be able to resume as normal.


Irish Water, who are now responsible for water networks, has set 2021 as the target date to eliminate all boil water notices in the country, and to reduce the leakage of treated water by 11%.  The targets are contained in a draft plan by Irish Water for managing water services over the next 25 years. In 2017, 42 boil notices were issued in 17 counties affecting 21,657 people. Half of these were short term notices, put in place for under 30 days. This was a significant reduction from 2016 boil notices with 83,044 people affected. To check the current status of water supplies in your area see the Irish Water website

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