THMs are a group of more than 60 chemicals, including chloroform — created as by-products when peaty water or water with excessive algae is treated with chlorine to disinfect it. They are considered potentially carcinogenic but the HSE has downplayed the risk, saying such studies are “inconsistent”. However, boiling water with high levels of THMs can actually increase their potency.
In Carraroe, Co Donegal, boil water notices have been issued to up to 4,700 consumers due to the presence of cryptosporidium in the water. However, water in the area also has historically high levels of potentially toxic THMs due to widespread use of chlorination to disinfect the water.
“Boiling water that contains high levels of THMs creates an imminent danger to public health because the volatile chemicals are released and absorbed by the skin and through inhalation at a rate 5-15 times faster than drinking the water,” said FOIE director Tony Lowes.
As a result of the situation in Donegal, FOIE has filed a complaint to the EU Ombudsman about Irish Water’s failure to be more upfront to the public about the dangers of THM exceedances. They believe this latest complaint could lead to the reopening of its 2011 complaint which led to Irish Water publishing all THM breaches on its website.
In recent weeks, it emerged that up to 380,000 consumers across the country may be drinking water with excessive THMs. The affected water sources are in various parts of the country, with several in Kerry and Cork, Kilkenny City, Waterford, Wicklow, Meath, Mayo, Roscommon, Donegal, and Galway.
Mr Lowes said: “Given that studies have suggested THM exposure in pregnant women can adversely impact birth weight, and even lead to more serious consequences, the failure to at least warn these women to ventilate the area and avoid the toxic fumes would appear to border on the negligent.”
However, Irish Water has argued that the risk from cryptosporidium is more real than that from THMs.
“Water that is not properly disinfected creates an unacceptable and very real level of risk of infection from water borne pathogens like E.coli and cryptosporidium,” said an Irish Water spokesperson. “In reference to THMs, the WHO has advised ‘adequate disinfection should never be compromised in attempting to meet guidelines for THMs. We have been advised that a balance must be struck between an uncertain, small and long-term risk associated with elevated THMs and the significant, large, immediate and serious risks associated with inadequate chlorination such as e.coli outbreaks.”
US environmental campaigner Erin Brockovich waded into the row in this country over THMs last month warning people not “to be fooled by this dodge of responsibility and factual sharing of information by your government”.
Long-term exposure to THMs include an increased risk of certain cancers, such as bladder and colon; reproductive problems such as miscarriages, birth defects, and low birth rates; and damage to the heart, lungs, liver, kidney, and central nervous system.