THE UNKNOWN EQUATION

by

SYLVIA MORTOZA

Attempts to find a solution to the arsenic problem - solutions that would not only be effective but also cost-effective has turned people's attention to the use of aluminium sulphate as coagulant. The amount of aluminium sulphate in water is recommended as 300 mg/L as coagulant (reducing agent). The ideal pH range is 7-8. Initial 30-sec rapid mixing, 10-min slow mixing for flocs, and 1-hour retention time prior to filtration (a cotton cloth may be used for filtering). The use of a similar amount of bleaching powder (premixed) works as an oxidising agent to complete the other half of the electrochemical reaction. The reported result is an 80% removal of arsenic and 97% removal of iron. The presence of iron (III) helps the process, thus the process is named as iron-cum-arsenic removal using a

precipitation-coagulation method.

Long believed to be harmless, and as the people of Bangladesh have been using it for water clarification for years, particularly in those areas where the iron content is high, aluminium sulphate was thought to be culturally acceptable for reducing arsenic in groundwater. With evidence fast accruing that its use for water clarification could be dangerous, we now have to ask ourselves just how harmless it really is?

However, aluminium is the third most common element in the Earth's crust and this fact alone has made it acceptable and is used to forward the claim that aluminium salts cannot pose an environmental hazard. The fact is different for, even under normal environmental conditions, the toxic effects of aluminium are responsible for enormous ecological damage and economic losses throughout the world. It is also implicated in a number of devastating human morbid conditions as well as being a recognised complicating factors in renal dialysis. Of specific concern are the natural consequences of acid rain, the effects of development activities in areas with naturally-occurring acid-sulphate soils and the impacts resulting from the use of aluminium salts in industrial processes such as water treatment.

When mixed with water, aluminium sulphate has a strongly acidic reaction: Al2(SO4)3 . 14H2O + 6H2O = 2Al(OH)3 + 6H+ + 3SO42- + 14H2O

The hydrogen ions released combine with alkalinity anions (HCO3-, CO32-, and OH-) to produce carbon dioxide and water and lower the pH (Boyd, 1979). Provided that the pH can be controlled by adding sufficient cations (in the form of lime slurry in water treatment practice), the hydroxide remains as a colloidal solid, and acts as a filter for particulate matter in the raw water supply. However, if the pH drops to around 5 or less, the hydroxide redissolves, producing a clear extremely acidic solution.

This is of primary importance to us so before we dismiss it "out of hand" we should also be aware of some of the other applications in common use that involve aluminium. For example, aluminium hydroxide is a component of many anti-perspirant formulations. Although exposure to aluminium salts on the skin of mammals has long been considered to present little or no risk of absorption or of surface damage, hence the widespread use of aluminium hydroxide in anti-perspirants, transdermal transfer of aluminium from aluminium chloride solution across the skin and into the hippocampus in the brain of mice has been recently demonstrated. (Anane et al., 1995).

Aluminium also forms an important constituent of "ant-acid" remedies for the relief of stomach acidity. In its latter use, the possibility that it might be taken with drinks containing chelating agents such as citrate and sugar might cause some surprise, since the ability of the chelated aluminium to pass into the blood stream is undoubtedly an important mechanism which permits the element to by-pass the supposed cellular barrier to absorption (Kruck and McLauchlan, 1988). The fact that aluminium in public water supplies and various medicines can pose a threat to public health has been known for more than 60 years (Betts, 1926).

Over the past decade, interest in the possibility of a link between aluminium and a number of encephalopathies has grown, fuelled particularly by attempts to discover the cause of the increasing frequencies of Alzheimer's disease, commonly called senile dementia, in western populations. Empirical evidence to support a link between average

levels of aluminium in drinking water and the incidence of Alzheimer's disease in Norway was provided by Flaten (1986), and more convincingly in England and Wales by Martyn et al (1989). The latter reported that the frequency of Alzheimer's Disease is increased by 50% when the average level of aluminium in the public water supply reaches 0.11 mg/l.

Higher average aluminium concentrations were not however, found to result in a further increase in the frequency of the disease. To place this in context, the Maximum Admissible

Concentration (MAC) which is accepted in the European Community for aluminium in public drinking water is 0.2 mg/l.

But as the accumulation of aluminium in areas in the brain in which neurofibrillary tangles develop was demonstrated by Perl and Brody (1980), and in senile plaque by Candy et al (1980), both features are diagnostic of Alzheimer's Disease, and as aluminium also appears to be implicated in similar neuritic tangles in Down' syndrome, and to be one of the factors in the amyotrophic lateral sclerosis complex of Guam and the Kii Peninsula of Japan, it could be we are risking people's health by advocating the use of aluminium

sulphate in arsenic reduction.

Although there is some evidence that some of the factors involved in these encephalopathies and in aluminium toxicology may be genetic, nevertheless the wide use of

aluminium sulphate in the treatment of arsenic-contaminated groundwater is of concern as exposure to aluminium from water sources is far more common than has been acknowledged. The gene which produces the protein has been identified and is located on chromosome 21. However as the main source of aluminium which can enter the blood is from drinking water we cannot also pass this off as simply a genetic problem.

When aluminium sulphate is dissolved in water, it forms remarkably complex semi-solid hydroxides, releasing sulphuric acid as it dissolves. If enough aluminium sulphate

is added to water, the acidity of the water may increase to such a level that these compounds are redissolved. The process of flocculation using aluminium sulphate is not entirely stable as changes in the water quality can disturb the formation and management of the hydroxide sludge blanket. This may disintegrate suddenly, releasing large quantities of

semi-solid aluminium hydroxide into the water supply. If this water is drunk, then hydrochloric acid released from specialised cells in the stomach immediately dissolves the

hydroxide, forming an ionic solution of the chloride.

Discovery of the dangers of using aluminium sulphate for water treatment processes came as a result of the contamination in 1988 of the public water supply to the town of Camelford in Cornwall, England when the solution used in the purification of drinking water was accidentally discharged into the treated water tank at the Lowermoor Water

Treatment Works. This water treatment works supplied more than 7,000 properties and at least 20,000 local consumers and tourists in North Cornwall but despite the repeated

reassurances that aluminium in the drinking water posed no health hazards, many people in Camelford did in fact suffer from persistent medical problems, some of which are still so

severe that the victims are no longer able to lead a normal life, or operate their businesses.

An argument frequently put forward to deny that orally administered aluminium can be harmful is that the widespread use of antacids, (which may contain up to 50 times the normal daily intake of aluminium in a single dose), causes no observable harm. In fact the gut wall is by no means such an effective barrier as this optimistic view would suggest;

children with renal failure who are on oral treatment with aluminium hydroxide certainly can develop hyperaluminaemia, and dialysis encephalopathy may develop despite the fact that they may not be undergoing dialysis (Griswold et al, 1983).

Aluminium is mainly present in unprocessed foods as a relatively insoluble aluminosilicate, or else associated with chemicals such as tannin which form complexes which are very resistant to digestion. Such foods do not provide a significant quantity of aluminium which can be absorbed into the bloodstream. However a wide range of processed foods often contain relatively simple ionisable aluminium salts. For example sodium aluminium phosphate and sulphate added to baking powders may account for as much as 15mg of aluminium per cake, equivalent to two to three times the normal adult

daily intake.

The health risks of using aluminium sulphate in the purification of public water supplies is a potential health hazard and as it is also linked to the water fluoridation controversy, because the formation of the fluoro-aluminium complex appears to present yet more risks to brain chemistry, in those areas where we have flouride, this is of added concern. Obviously the risks from aluminium poisoning cannot be easily brushed aside for, although the Cornwall and Isles of Scilly Health Authority claims only traces of aluminium could be absorbed from the gut, regardless of the quantity swallowed, and even this would be rapidly removed from the body, this is simply not true, as an investigation immediately after the incident by Dr Richard Newman, a local GP and Doug Cross demonstrated.

These two eminent researchers found marked short-term increases in mouth ulcers, upper gastric tract complaints, diarrhoea, severe lethargy, nausea and vomiting. Mild arthritics reported substantial increases in the pain of their condition, and there was also an increase in reports of more persistent non-arthritic bone pain and of skin rashes (Cross and Newman, 1988). About four months after the incident, Newman noted that a number of his patients reported memory problems and impaired concentration and judgement (Newman 1990). After substantial lobbying by CSAP, arrangements were made for specialists to examine a small number of victims who appeared to be particularly seriously affected. Bone biopsies of two residents showed a discrete band of aluminium deposition consistent with a single, short-lived exposure (Freemont, 1990). Taylor (1990) found that 21 of 31 post-incident referrals showed significantly increased blood aluminium levels up to one year later; these included those patients who also had evidence of aluminium deposition in their bone.

Cognitive impairment in a group of 11 Camelford referral patients complaining of impaired memory was found to be consistent with minor brain injury (McMillan - 1990), and this was not attributable to emotional factors. Three-quarters of 32 referral patients had significant memory deficits, which had severely impaired their ability to run their businesses or had adversely affected their styles of living (Wilson - 1990). Newman considers that there are at least fifty additional cases which have not been examined by the clinical psychologists.

There is now convincing evidence of a direct link between aluminium in drinking water and the incidence of Alzheimer's disease, even at levels that are less than half the recommended EC maximum level, therefore using aluminium sulphate for reducing arsenic in groundwater and using aluminium pans for cooking, especially for cooking acidic foods, is liable to result in excessive contamination by the metal. As aluminium in drinking water is either dissolved or readily brought into solution, its bio-availability may therefore be much higher than aluminium from other sources. Although no studies have been undertaken on the effect of adding aluminium sulphate to arsenic-contaminated groundwater, the evidence demands we proceed with caution.

The literature on aluminium-related toxicity hazards now clearly indicates a probable causal link between environmental aluminium and a number of serious, irreversible neurological conditions - and as we are already ingesting arsenic from groundwater, we should proceed with great caution for the weight of scientific opinion today is that aluminium in drinking water is far more 'bio-available' than that in food, and that some people are genetically less competent in dealing with it when it does enter the blood. There is also evidence from Camelford that aluminium overload, even from relatively short periods of acute exposure, can lead to persistent neurological damage which can dramatically reduce the ability of individuals to cope with the problems of domestic and commercial life.

The various biochemical pathways responsible for absorption of aluminium from the gut, transfer through the body, and accumulation in bone and nerve tissues have been

documented in a recent review of the mechanisms of aluminium neurotoxicity. (Kruck and McLaughlan, 1988). Autopsies of victims of Alzheimer's disease have revealed excessive amounts of aluminum and silicon in the brain, this suggests that excessive amounts of aluminum in the diet, combined with a lack of several essential minerals, directly or indirectly predispose one to Alzheimer's disease. The threshold level for increased Alzheimers in relation to aluminium in drinking water is only half of the EC Maximum Admissible Concentration (MAC) - 0.2 mg/l.

The problem is that aluminium hydroxide - the floc that separates out when the sulphate is mixed with water - is amphoteric - i.e., it dissolves in both alkaline and acidic solutions. When aluminium sulphate mixes with water it releases both aluminium hydroxide solid AND sulphuric acid. If too much aluminium sulphate is added, the acidity due to the sulphuric acid becomes so high that the hydroxide re-dissolves. This gives a clear - and apparently pure-looking - solution which people think is safe to drink. It is not!

Since so many people are already vulnerable to arsenic poisoning, as well as iodine deficiency, it is totally unacceptable to discount exposure to a known neurotoxin - and one with such devastating results - on people already under severe environmental challenge. Experts say quite emphatically that exposure to environmental aluminium is one of the great disasters of our time, and one which will eventually become much more widely accepted as the evidence continues to accumulate. Faced with one disaster already, we do not want to be faced with another. The presence of fluoride in water contaminated with aluminium can be even worse for it can lead to a very dangerous condition - exposure to the alumino-fluoride complex. This is extremely worrying because it links to the very severe damage that can be caused by free radicals. The question that now needs answering is - will the use of aluminium sulphate for reducing arsenic in water have an adverse effect on the people who are already suffering from arsenicosis, especially those who have reached the point of no return?

Acknowledgements:

1) Doug Cross - Environmental Analyst and Consultant.

2) Sabir Majumder Ph.D.

No. of words: 2409