Human activity releases a large number of chemical pollutants into the environment, many of which are harmful to human health. Some chemicals that are particularly noted for their ability to persist in the environment once released and for their harmful effects on health and the environment, are collectively known as “persistent organic pollutants” (POPs). These include many pesticides, dioxins, polychlorinated biphenyls (PCBs), furans, polycyclic aromatic hydrocarbons (PAHs), brominated flame-retardants, and organometallic compounds. Their chemical properties which often include chemical stability, low volatility, low water solubility and high lipid solubility, mean that once released they don’t break down in the environment but accumulate in soil and water and pass into the food chain. Bio-accumulation can then occur where they build up in the fatty tissues of animals, the concentration in the tissues increasing up the chain.
The effects on human health caused by POPs vary according to the compound, but potential concerns include cardiovascular disease, disruption of the endocrine, reproductive, and immune systems and neurobehavioral disorders, and some are confirmed or suspected carcinogens.
UNEP issued a press release on 7 December 2010 about the findings of a major international study on how climate change increases the planet’s vulnerability to persistent organic pollutants (POPs). The study, “Climate Change and POPs Inter-Linkages”is the first systematic and authoritative review of the impact of climate change on the release of POPs into the environment, their long range transport and environmental fate, and human and environmental exposure.
Katarína Magulová, Programme Officer of the Secretariat of the Stockholm Convention is quoted in the press release saying
“Climate change increases the planet’s vulnerability to persistent organic pollutants, by increasing emissions and the bio-availability of POPs, and thus the potential for bio-magnification through the food chain, one of the chief pathways of human exposure to POPs,”
According to the study, global warming contributes to a higher frequency of extreme weather events, which can cause severe flooding, triggering the secondary emissions of POPs. The higher temperatures resulting from climate change can also make wildlife more sensitive to exposure of certain pollutants.
An international treaty on POPs, the Stockholm Convention on Persistent Organic Pollutants, was adopted in 2001 and entered into force in 2004. The treaty, which is administered by The United Nations Environment Programme (UNEP), requires Parties to take measures to eliminate or reduce the release of POPs into the environment. Further details will be available when the findings are presented to the 5th meeting of the Parties to the Stockholm Convention in April 2011.
These findings illustrate the complexity of what happens when pollutants are released to the environment. Some can cause short term effects on humans – for example irritation due to inhalation of gaseous pollutants such as sulphur dioxide – while other pollutants, such as POPs, exert their effects over a longer timescale. In both cases the pollutants cause direct effects on health. However pollutants can also cause indirect effects. A particularly important example is provided by carbon dioxide. This is a major pollutant, but at atmospheric concentrations does not cause any direct effects on health. However, as the main “greenhouse gas” contributing to climate change it is indirectly responsible for a wide range of adverse health effects. There’s a good summary of the impacts on health on the WHO website. The findings from the study provides another example to add to the list.
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