Dioxin Levels in the Irish Environment lower

Date released: Oct 18 2005

The EPA today reported that dioxin levels in Ireland in 2004 were 33% lower than in 1995 and 20% lower than in 2000. In its Report entitled “Dioxin Levels in the Irish Environment (Summer 2004)” the EPA survey confirmed that dioxin levels in Ireland remain among the lowest in Europe.   The Report’s findings are based on a survey of dioxins and dioxin-like compounds in cow’s milk undertaken in mid 2004.

The reduction in dioxin levels is in line with similar reductions across Europe.  Major advances in combustion technology, measures such as the abolition of leaded petrol and ever-more stringent environmental regulation and enforcement are believed to have had a considerable role in these reductions.  This is the second successive reduction in dioxins relative to comparable surveys undertaken in 1995 and 2000.

The 2004 survey was carried out between late May and early July, during the peak outdoor grazing season.  A series of milk samples was taken from representative regional dairies (24 samples) with additional samples taken from regions of more intensive industrial activity (13 samples).  Cows’ milk is considered to be a particularly suitable medium for assessing the presence of dioxins in the environment.  Cows tend to graze over relatively large areas and these compounds, if present, will concentrate in the fat content of the milk.

The investigation showed that the concentrations of dioxins were uniformly low by international standards.  The levels also showed a clear reduction over a nine year period in line with international trends.  The survey confirms the continuing low levels of dioxins and dioxin-like PCBs in the Irish environment.

The results of the survey were as follows:

  • The average 2004 dioxin concentration corresponds to reductions of around  33%  since 1995 and 20% compared with 2000. This reduction is in line with international trends.
  • There were no unusually high values meriting particular attention in any of the samples though there was a tendency towards slightly higher values along the more urban East Coast.
  • Concentrations were uniformly low by international standards.  A total of 37 samples were taken and the levels for dioxins in milk fat ranged from 0.06pg to 0.45pg per gram of fat or an average of 0.195pg of WHO Toxic Equivalent.  This compares very favourably with the EU limit of 3.0pg WHO-TEQ/g for dioxins in milk and milk products.
  • The highest dioxin levels found in Ireland were less than one sixth of the EU Limit.
  • Dioxin-like PCBs (polychlorinated biphenyls) were also measured and - in line with the 2000 survey and with other studies -the PCB levels accounted for around half the total dioxin figure.

Note: The WHO Toxic Equivalent (WHO-TEQ/g) referred to above is the current internationally recognised system for comparing dioxin toxicities of different samples.

What are Dioxins?

Dioxins form a group of some 210 closely related, complex organic compounds, the vast majority of which are considered to have little environmental significance at the levels normally encountered. However, 17 of these substances have been shown to possess a very high toxicity, particularly in animal tests. The toxic responses include dermal effects, immunotoxicity and carcinogenicity, as well as reproductive and developmental toxicity. Dioxins arise mainly as unintentional by-products of incomplete combustion and from certain chemical processes. Similar effects are caused by some of the dioxin-like polychlorinated biphenyls (PCBs) and in order to conform to current practice, testing for these compounds was also included in this programme. 

Sources of Dioxins

Although dioxins and PCB’s are not produced intentionally except for research and analysis purposes their formation is often a by-product of many anthropogenic and natural activities.  Some significant sources internationally are:

  • Accidental fires
  • Backyard burning of household waste and bonfires
  • Cement kilns (especially where hazardous waste is co-incinerated)
  • Chlorine bleaching of wood pulp
  • Coal fired power plants
  • Copper production
  • Forest fires and other natural fires
  • Incineration of medical waste
  • Incineration of municipal or  hazardous waste
  • Production of steel
  • Residential combustion (especially where wood is used)
  • Sinter plants
  • Traffic

In Ireland, it has been estimated that in 2000 over 75% of the Dioxin load to the atmosphere came from uncontrolled combustion processes such as backyard burning of waste or forest fires. (Dames & Moore report 2002)

The report can be found at www.epa.ie/downloads/pubs/air/quality