| FACS Newsletter 1/2003
The International Year of Freshwater (2003) :
Key issues for the Asia Pacific Region
Barry N Noller,
President of FACS 2001-2003
National Research Centre for Environmental Toxicology (EnTOX)
The University of Queensland
9 Kessels Road, Coopers Plains, QLD 4108, Australia
1.
Introduction
2.
Declaration of the International Year of Freshwater
3.
Significance of Water Use
4.
Some Significant Regional Impacts
5.
Some Examples of Groundwater Contamination
6. Risk Assessment as an Appropriate Methodology
7.
What is Risk Assessment
8.
Hazard Identification
9.
Dose-Response
10. Risk
Characterization
11.
Lessons from historical examples
12.
Conclusions
1. Introduction
UNESCO designates the year 2003 as the International Year of Freshwater. Increasingly freshwater or drinking water becomes a more valuable commodity, which can longer be taken for granted. The Global Summit held at Johannesburg in 2002 clearly demonstrated that availability of freshwater was equally as important as greenhouse phenomena when considering issues of importance to mankind.
There is a range of contaminants, which need to be considered and their control understood in order to guarantee freshwater supply. These can be both abiotic and biotic in origin.
Naturally occurring substances can exist in equilibrium with groundwater, eg from mineralization. Some of the best examples available relate to the incidence of arsenic in groundwater and its tragic consequences in countries such as Bangladesh, India, China, Taiwan and Thailand. Other substances such as blue green algal toxins contaminate most surface waters to some degree.
High population density and the resultant creation of nutrient waste can lead to contamination of groundwater sources by nitrogen compounds, particularly nitrate, and biotic contamination from pathogens and viruses. Other anthropogenic compounds such as persistence organic pollutants have become significant pollution problems of groundwater.
Recycling of water is seen as a cost-effective means of guaranteeing water supply and reducing its cost. However more subtle concentrating steps leading to human exposure from a variety of chemicals, collectively called endocrine disrupters and other pharmaceuticals, are occurring. Increasingly man-made chemicals are finding their way into recycled water creating undescribed effects in people.
The definition of the scope of human exposure is seen to be an increasing problem associated with the guarantee of freshwater supply. The understanding of these problems is a key to guaranteeing water supply to mankind.
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2.
Declaration of the International Year of Freshwater
The United Nations General Assembly (Resolution 55/196) proclaimed 2003 as the International Year of Freshwater.
The essential elements of the resolution are:
- To increase awareness and importance of sustainable freshwateruse, management and protection; and
- Calls upon governments and agencies to volunteer contributions and other focus of support in order to advance the activities of the International Year.
Clearly both elements are relevant to the Asia-Pacific region. The FACS can play a role in helping to bring together the involvement of member societies to support the UNESCO initiative.
The International Year of Freshwater also seeks to:
- Provide opportunity to accelerate integrated resource management;
- Promote existing activities and show new initiatives in water resources; and
- Follow on agreements reached at the World Summit on Sustainable Development, Johannesburg, September 2002.
It was a significant outcome of the Johannesburg 2002 meeting that a basic commodity like freshwater was to be given such prominence as a matter of high priority to the global community. Clearly the global relevance also applies to the Asia-Pacific region.
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3. Significance of Water Use
Currently the World¡¯s 6 billion people use 54% of the accessible freshwater, both ground and surface waters. It is expected that by 2005 the demand will increase to 70%.
Currently 69% of water for human use on an annual basis is used by agriculture (mostly irrigation) compared with 23% by industry and 8% by domestic use.
Agriculture
About 69% is currently used for agriculture. Over pumping currently exceeds replenishment, a clear case of needing rectification. For example 1-3m3 water is needed to yield 1kg rice; 1000tons water needed to produce 1ton grain. Such quantities of water indicate why the consumption for agriculture is such a large proportion of total.
A disastrous environmental effect of poor drainage and irrigation practices has created water logging and salinization of 10% irrigated lands. If not controlled or reversed, this can lead to desertification in marginal lands.
Agriculture is responsible for most of the depletion of groundwater together with 70% of the pollution. The addition of nutrients and contaminants in fertilizer such as cadmium, pesticides and herbicides and specific micro contaminants from the use of pharmaceuticals and other specific chemical use. The cocktails produces in today¡¯s irrigation runoff are the outcome of enhanced food production, but not all may be beneficial to retaining the water resource in the future.
Industry
The World withdrawal for water use comprises 22% of total. High-income countries account for 59% of total compared with 8% of total for low income countries.
By 2005 it is predicted that the industrial component will be 24% for total freshwater withdrawal. 300-500 million tons of heavy metals, solvent, toxic sludge and other wastes are accumulated annually from industry including most of the organic pollutant load.
A few other specific details are that:
- 80% of industry waste is produced in the industrialized countries; and
- In Developing countries 70% of industrial waste in dumped.
Energy
Hydropower accounts for 19% of total electricity production. Although popular in the past, dams are longer a preferred method for retaining water resource.
The World Commission on Dams (2000) states that the record is not good. This is due to the enormous energy cost of creating dams and the significant damage to catchment ecosystems from preventing free river flow.
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4.
Some Significant Regional Impacts
High Population Impacts in River Valleys
The most densely populated places on Earth are found on the Asia-Pacific Region. In the Indian Sub-continent lies the Ganges-Bramaputra river valley; in China the Yangtze River. The significant land use in these catchments and flood plains results in the transfer of huge quantities of suspended material comprising soil, sewage and a whole host of absorbed constituents. Soluble components are leached and transported to sea. Huge plumes are evident from the estuaries of these rivers to considerable distances out to sea, evident from satellite images.
Gross effects of salinity on land degradation
The sustained use of irrigation is now demonstrated to cause salt rise when soil becomes water saturated. This is particularly serious in several parts of Australia where there is a pre-existing salt horizon at depth from earlier marine episodes resulting in surface expression from salt rise.
Unless the practice of salt rise and leaching of salt is controlled and prevented the utilization of agricultural land for purposes of food production is minimized or eliminated. The situation has been exacerbated through the removal of native vegetation to undertake agricultural practices. Previously salt was controlled naturally through endemic vegetation eliminating water as vapor and keeping the soil horizon dry.
The most extreme example in the region is at the Aral Sea in Uzbekistan where over zealous use of water for irrigation purposes has caused the lake to be divided and become polluted with significant pesticide and nutrient residues.
Such whole of scale ecological damage was not considered when the economic benefit of irrigation was first undertaken. The finite balance of nature is clearly demonstrated in this case, as the once common fishing industry at the Aral Sea has ceased.
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5.
Some Examples of Groundwater Contamination
Arsenic in Groundwater
The observations of the last 20 years have been that the presence of arsenic in drinking water derived from groundwater poses a significant health risks. This is because sustained intake of arsenic results in skin keretosis and culminates in skin and other cancers. The evidence of significant episodes in West Bengal, India and Bangladesh has confirmed that a detailed understanding of natural processes affection availability of drinking water is necessary as well as knowing if polluting substances are present even from natural sources.
The example of West Bengal and Bangladesh is an example of a tragic situation. The WHO took the step of reducing the drinking water criteria for arsenic from 50µg/L down to 10µg/L based on overwhelming evidence for significant occurrence of skin and other cancers. In Australia the accepted drinking water criteria for arsenic is now 7µg/L based on body weight being 70kg for an adult.
In Bangladesh it is now established that the range of arsenic concentration in groundwater is <1-2500µg/L. The arsenic is now clearly shown to be natural in origin being associated with arsenopyrite material during geological times. Accessing of groundwater for drinking purposes has resulted in oxygenation of the arsenic-containing sequences that have released arsenic into solution. It has now been show that the presence of high concentrations of phosphates and organics has accelerated the oxidation process.
Whilst it is important to understand the mechanism of release of arsenic, it is equally important to desire means of removing the arsenic, which can be afforded by local village people. In a country like Bangladesh there needs to be solutions which can be afforded by all peoples.
Anionic Substances
Anionic species may be become significant pollutants in groundwater sources if they are readily available. This is because anionic species are less likely to be complexed by substrate materials.
A clear example of a natural problem is that of fluoride and fluorosis which is evidence in many parts of India and certain parts of China.
A classic example of an anionic contaminant to groundwater has emerged in the U.S.A. where perchlorate has entered aquifers as a results of rocket fuel manufacture. This is in fact the reverse situation to that of arsenic where natural processes prevent the perchlorate from being attenuated. A clear lack of understanding of the potential of such a simple substances to become a significant pollutant is clearly evident.
Perchorate is highly soluble and is poorly adsorbed. Although it may be present in fertilizers derived from natural sources such as from Chile it is derives primarily from rocket fuel manufacture. There is a health effect debate regarding perchlorate in drinking water, emphasizing the need to have human health risk assessment data on potentially contaminating substances. The pathways for microbiological degradation of perchlorate are known but need to be better applied.
Unwanted effects from useful compounds
The classic example that emerged is the substitution of MTBE (methyl tert-butyl ether) in petrol as an oxygen source to replace the use of lead alkyl compounds in petrol. What was developed as a significant advancement in air pollution control coupled with unprecedented growth in use until the last few years has now culminated in the banning of the substance in the USA.
The reason for this apparent contradiction in use stems from the significant side effects to the environment, particularly intrusion into groundwater. It has become clear that there is extensive transfer of MTBE into groundwater.
The significant properties of MTBE are:
- It is very soluble in water (5000mg/L) compared to hydrocarbons
in petrol;
- It cause a taint in groundwater which causes more significant health effects at higher concentrations; and
- It is not readily degraded by micro organisms.
The collective effect of MTBE transfer to groundwater is the significant contamination of this kind of water resource where MTBE has been included as a petrol additive.
A specific enhancing step of this kind of pollution has been that most underground hydrocarbon storage tanks leak. The long-term effect of this kind of polluting process coupled with the properties of MTBE was not fully assessed before its widespread application became commonplace.
Micro contaminants in recycled water
It has been clearly recognized in many countries that water needs to be recycled. This has been the practice in Europe for many years. In countries like Australia this has not been the practice and drinking water quality has been the water industry norm. Clearly this practice is unsustainable and the need to re-use water is a necessity. Based on previous discussion with contaminants it is reasonable to propose what hazards might exist in re-cycled water. There is currently an intensive evaluation being undertaken of the potential of micro contaminants affecting drinking water quality, than the most common, expected contaminant - pathogens.
There are a significant number of other potential contaminants. It is recognized that a number of these may be quite difficult to measure as they can exist at low concentration yet still be significant with regard to health effects.
Detailed studies have revealed that most effluent derived chemical contaminants have much lower log Kow, values than hydrophobic contaminants such as PAH¡¯s and PCB¡¯s.
There are significant health risk questions with regard to a number of these substances.
Clearly the application of recycled water warrants detailed health risk assessment before it can be given as absolute clearance.
The question is then one of experience the application of strategies to prevent the disasters cited in other examples. There are some lessons to be learnt for the
Asia-Pacific region.
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6. Risk Assessment as an Appropriate Methodology
The selection of examples of specific ¡°contamination¡± episodes in groundwater shows the need for an ongoing focus to understand clearly the pollution processes that are likely to occur. This brings the focus of what is needed to one of understanding the risks involved with bringing substances in contact with groundwater and surface water resources. The list of examples is too numerous to ignore such incidents.
In this year of International Freshwater there is clearly a role of responsibility for everyone. There is clearly an ongoing need for education on how to minimize the effects of pollution at all levels.
The key question is how to deal with contamination issues in freshwater.
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7. What is Risk Assessment
Risk assessment is a process for organizing what needs to be known about health risk and developing judgements about risk.
It commonly follows the following steps:
- Hazard identification
- Dose-response (toxicity) assessment
- Risk characterization.
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8. Hazard Identification
The process must distinguish hazard from risk. Hazard is the potential to cause harm of some magnitude with specified consequences. Risk is the likelihood that a hazard will arise within a specified time horizon. Hazard identification evaluates whether an agent is capable of causing the specified damage.
The nature of hazard is needed in order to be able to assess risk. Priorities for action should be based on risk rather than hazard.
For example arsenic is a hazard in any groundwater source.
Actions should be based on an assessment of how likely arsenic is to induce skin keratosis and subsequently skin cancer. The key question is what is the risk of cancer associated with this source of groundwater.
Gaps in scientific knowledge and data mean that risk assessment involves many choices and assumptions. Different choices can have a large influence on estimates of risk:
- Exposure assumption
- Critical effect in non-cancer risk assessment
- Cancer bioassay for potency
Paracelsus (1567) stated: ¡°All substances are poisons: there is none which is not poison. The dose differentiates a poison from a remedy.¡±
Hazard identification has been initiated for many chemicals by showing an ability to change function, usually by means of in vitro tests. Hazard identification for most chemicals has not been completed by also proving to a credible scientific standard that the chemical is adversely causing: adverse effects at the level of the organism, its progeny, and/or (sub) populations.
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9. Dose-Response
Dose-response is the likelihood of harm that cannot be assessed without knowledge of what dose is required to cause any specific adverse effect. Dose-response assessment determines the quantitative relationship between exposure and illness. Where chemicals have been shown to cause adverse effects on ¡°an organism, its progeny and/or (sub) populations, rarely has a relevant quantitative relationship been established.
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10. Risk
Characterization
If we knew the dimensions of the risks it would be possible to realistically set priorities for action.
The basis for meaningful risk characterization of mixtures of constituents in groundwater does not yet exist, although a considerable about of information is available for discrete substances.
In many cases hazard-identification is incomplete. In most cases dose-response assessment is poor and exposure assessment is not focused. This makes complete risk characterization difficult to achieve.
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11.
Lessons from historical examples
The examples cited indicate that there are lessons to be learnt from both natural sources of contamination and man-made additions to sources of fresh water. In nearly every case there is clearly a lack of understanding of hazard identification based on an approach, which assumes that groundwater is safe to use as a drinking water supply.
Episodes of anthropogenic contamination of aquifers have simply not considered the consequences of the mobilities of chemical species, which are not readily absorbed on substrates. There are 2 key lessons to apply during the International Year of Freshwater:
- For groundwater and other sources which may be influenced by natural processes and natural contaminants a complete assessment of hydro-geological characteristic is required; and
- Where anthropogenic activities may give rise to losses of synthetic substances, their properties should be evaluated to predict if there is likelihood of their being any significant migratory behavior as a result of non-complexing properties or polar character.
If migration of unknown compounds in groundwater is predicted, then the dose-response relationships of such compounds need to be evaluated. The challenges are therefore related to the weighing any conflict with toxicological or other data for substances in groundwater and other sources of supply of freshwater.
Once established, management encompassing the range of risks needs to be applied. This needs to be followed communicating the uncertainty to manage, legislations and the public.
In developing countries, the challenge of such risk assessment is greater as such practices are less well developed. This is exemplified by the tragedy, which has occurred in Bangladesh. However, the developed countries are not entirely exempt as evidenced by the example of MTBE entering groundwater.
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12. Conclusions
The International Year of Freshwater has a clear obligation from all stakeholders to progress the understanding and improve the availability of freshwater to all people, particularly in the Asia-Pacific region.
There is currently inadequate hazard identification and dose-response knowledge available to complete a meaningful quantitative risk assessment for many chemicals present in freshwater. Trying to achieve zero risk for humans in relation to such compounds in beyond reality at this point in time. Hence an approach, which seeks to minimize risks, is more practical.
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