THE ENVIRONMENTAL CAUSES OF INTELLECTUAL DISABILITIES
Christopher Williams (UK)

• Introduction
• An awakened concern
• The full extent of EMID: The evidence jigsaw
  • Chemical factors
  • Malnutrition
  • Sub-clinical impacts
  • Statistical profile
• Costs and consequences
• Risk assessment
• Key implications

Introduction:

Millions of people now experience intellectual decline because of human-caused environmental change. Logically, protecting our intelligence should be a policy priority, but it is not. This study provides the first global assessment of Environmentally-Mediated Intellectual Decline (EMID) (Williams 1997).

Environmental medicine gives inadequate attention to the brain, concentrating on cancer and respiratory ailments which are simpler to diagnose and cure.

Priorities set by rich countries lead to an incomplete picture. Initiatives within the US Decade of the Brain largely concern neurotoxic environmental agents, such as lead, radiation, or PCBs (polychlorinated biphenyls). This omits the perspective of less wealthy nations - the dietary absence of vital environmental micro-nutrients such as iron and iodine.

There are no comprehensive statistics for EMID. There are figures concerning lead, PCBs, and micronutrient deficiencies, but it is not known if these figures describe the same or different people.

Risk-assessment is inadequate, creating an 'ignorance = safe' ethos.

An awakened concern:

The US Congress declared the 1990s The Decade of the Brain. The Congress Office of Technology Assessment produced key reports which claimed that environmental medicine had for too long concentrated on cancer, and ignored impacts on the brain, including dementia. The US National Research Council (NRC), marked a new medical discipline in the title of its report, 'Environmental Neurotoxicology', which expressed serious concern about the shortcomings of traditional risk assessment techniques when applied to the brain (National Research Council 1992).

While the US was concerned about the presence of hazardous environmental agents, UNICEF and the World Health Organisation (WHO) were addressing the absence, in poorer regions, of environmental micronutrients necessary for brain development (UNICEF 1994). Protein Energy Malnutrition (PEM) affects the intellectual ability of a third of all poor-nation children. This 'hidden hunger' often stems from land degradation and forest depletion compounded by population pressure. Improved literacy reduces population growth. But intellectual decline reduces literacy; thus increasing population and precipitating a regressive spiral.

The Decade of the Brain has seen these two parallel concerns. But because they reflect the rich-nation poor-nation divide, they have not been viewed together.

The full extent of EMID: The evidence jigsaw

Chemical factors:

Lead pollution and iodine deficiency are well-known causes of EMID, but there are many others (Barten 1992; and see Paul 1993; Grandjean and Landrigan 2006). For example, new evidence about hormone-disrupting chemicals (e.g. PCBs) emerged in 1996 (Colburn 1996).This could surpass the significance of lead, because these chemicals are persistent and there is no clinical treatment. In 1989, the impact of radiation on human intelligence was affirmed by the release of data concerning the A-bomb survivors in Japan (National Research Council 1990). Recent research links radiation releases from Chernobyl, Windscale and weapons testing with Downs Syndrome (Holowinsky 1993). Careless use of pesticides in agriculture and fish-farming is shown to have caused intellectual disabilities (Creizel et al. 1993).

The incidence of intellectual disabilities in polluted Soviet cities has increased twice as fast as in rural areas (Feshbach and Friendly 1992).

In Poland and the Czech Republic pollution has doubled the number of children needing special education, and halved the number of 'exceptionally gifted' children (Seligsohn 1994).

(For sources, see Further Reading).

Malnutrition:

Malnutrition has been an accepted cause of intellectual decline since the 1970s. More recent research concerning Protein Energy Malnutrition (PEM), and interrelated social factors, provides better understandings of 'sub-clinical' problems resulting from poor quality food (Waterlow 1993). High-yield 'Green Revolution' crops were introduced in poorer countries in the 1960s to overcome famine. But these are now blamed for causing intellectual deficits because they do not take up essential micronutrients. They have also displaced other nutritious indigenous food sources. In addition, UNICEF has found that the exclusive use of breast milk substitutes causes an IQ deficit of eight points (average IQ=100) (UNICEF 1993).

Cures are self-defeating. Poland uses crop varieties that take up less heavy metal from contaminated soils, but these varieties also take up less essential minerals. Resultant deficiencies can cause intellectual impairments directly and synergistically by increasing the human uptake of toxins from other sources (Seymour 1996).

Sub-clinical impacts:

'Clinical' outcomes (observable disability which can be traced to particular causes) are often indicative of much broader 'sub-clinical' impacts. In the 1970s, Herbert Needleman studied the sub-clinical impacts of lead in 3000 US children (Needleman et al. 1979). This revealed a strong link between high body-burdens of lead, and behavioural and intellectual difficulties recorded by teachers. In a follow-up study in 1988, Needleman found that the same children had displayed higher drop-out rates, lower class standing, increased absenteeism, and lower vocabulary and grammatical reasoning scores (Needleman et al. 1990).

There is no comprehensive statistical profile of EMID, but the following provides information gathered some ten years ago (Williams 1997: 18-27):

Costs and consequences:

In 1985, a US Congress study claimed that reducing the neurotoxic effects of lead on children would create a 'health benefit' of more than $100 million per annum (OTA 1990). Reducing lead from tap water from 50 to 20 grams per litre would save $27.6 million in medical care and $81 million in special education. The World Bank states that iron, vitamin A and iodine deficiencies reduce the Gross Domestic Product of developing countries by 5% (Seymour 1996).

Research in Ecuador found that when iodine deficiency causes average IQ to fall from 100 to 79 in a community, income halves (Correa 1980). The non-cash costs are also important. In communities where superstition prevails, a child born with an intellectual disability may spoil marriage opportunities for siblings and be seen as a punishment for a wrongdoing by the parents.

Risk assessment:

Environmental health priorities have stemmed from the 'easiest' science - visible outcomes such as cancer and respiratory ailments. Risk-assessment in relation to the brain is uniquely difficult. Only 10 per cent of the 70,000 commercially-used chemicals have been tested at all for neurotoxicity, 'and only a handful have been evaluated thoroughly' (National Research Council 1992). And assessments fail to account for interactions between chemicals. In Russian roulette, the revolver with one bullet represents a 1 in 6 risk. Under current EMID risk-assessment conceptualisations, if you don't know whether or not the gun is loaded, the result of the so-called risk assessment is 'safe'.

Assessment of toxicity in humans uses a rich-nation 'average human' model, which is often far from 'average' and sometimes far from 'human' (based on the white, young, well-fed, well-housed, male mouse). Although an uncertainty factor is added, this is just a guess which ignores known vulnerabilities.

As a result, so-called 'safe levels' for exposure to neurotoxins differ significantly between countries. Why is the UK standard for lead in tap water five times less strict than the WHO standard? Other figures for lead could imply that the UK brain is 17 times more robust than that of Americans - or 17 times less valuable (Wilson 1983).

The key implications are:

• Policy-makers should recognise the existence of environmentally-mediated intellectual decline. Not least, there is a need for greater acceptance of, and support for, people who have intellectual difficulties.
• Preventive environmental health policy should prioritise the brain, because it is the most vulnerable and valuable human asset. As a double dividend, better standards would provide benefits in other areas.
• The costs for education and health services, and a nation's intellectual resources, mean that EMID needs to be central to environmental management and risk assessment.

With the global population set to double in forty years, it seems reasonable to claim that we will all survive better if the potential of our intellectual resources is maintained at an optimum level. The prognosis is that this potential is under threat.

Further Reading

Grandjean, P. and Landrigan, P. J. (2006) Developmental neurotoxicology of industrial chemicals. The Lancet 368 (9553), 2167-2178.

National Research Council (1992) Environmental neurotoxicology. Washington DC: National Academies Press.

Paul, M. (ed) (1993) Occupational and environmental reproductive hazards: a guide for clinicians. Baltimore: Williams & Wilkins.

Williams, C. (1997) Terminus brain: the environmental threats to human intelligence, Cassell: London.

WWF-UK (2004) Compromising our children: chemical impacts on children's intelligence and behaviour. (Download PDF)

References

Barten, F. (1992) Environmental lead exposure of children in Managua, Nicaragua: an urban health problem. The Hague: CIP-Gegevens Koninklijke Bibliotheck.

Colburn, T. (1996) Our stolen future. New York: Dutton, Penguin.

Correa, H. (1980) 'A cost-benefit study of Iodine supplementation programmes for the prevention of endemic goitre and cretinism' in J. B. Stanbury and B. S. Hertzel, (1980) Endemic goitre and cretinism: Iodine nutrition in health and disease, John Wiley: New York.

Czeizel, A. E, Elek, C., Gundy, S., Metneki, J., Nemes, E. et. al. (1993) Environmental trichlorfon and a cluster of congenital abnormalitites. The Lancet, 341, 539-42.

Feshbach, M. and Friendly, A. (1992) Ecocide in the USSR: health and nature under siege. London: Basic Books.

Global Security Programme (nd) Environmentally-mediated intellectual decline (EMID): a selected interdisciplinary bibliography. Cambridge: University of Cambridge.

Grandjean, P. and Landrigan, P. J. (2006) Developmental neurotoxicology of industrial chemicals. The Lancet 368 (9553), 2167-2178.

Holowinsky, I. Z. (1993) Chernobyl nuclear catastrophe and the high risk potential for mental retardation. Mental Retardation, 31 (1), 35-40.

National Research Council (2006) Health effects of exposure to low levels of ionizing radiation (BEIR VII). Washington DC: National Academies Press.

National Research Council (1992) Environmental neurotoxicology. Washington DC: National Academies Press.

Needleman, H., Schell, A., Bellinger, D., Leviton, A. and Allred, E. N. (1990) 'The long-term effects of exposure to low doses of lead in childhood: an 11-year follow-up report' New England Journal of Medicine, 322 (2), 83-8.

Office of Technology Assessment (1990) Neurotoxicology: identifying and controlling poisons in the nervous system OTA-BA-436. Washington DC: US Government Printing Office.

Paul, M. (ed) (1993) Occupational and environmental reproductive hazards: a guide for clinicians. Baltimore: Williams & Wilkins.

Rogan, W. J. and Gladen, B.C. (1993) 'Breast feeding and cognitive development'. Early Human Development, 31, 181-93.

Seligsohn, D. (1994) 'Insidious poisoner at home', The European, 4-10 February, 16.

Seymour, J. (1996) 'Hungry for a new revolution'. New Scientist, 2023, 32-7.

UNICEF (1993) Global child health 1(2), 1.

UNICEF (1994) Annual report. New York: UNICEF.

Waterlow, J.C. (1993) Protein-energy Malnutrition. New York: Hodder Arnold.

Williams, C. (1997) Terminus brain: the environmental threats to human intelligence, Cassell: London.

Wilson, D. (1983) The lead scandal: the fight to save children from damage by lead in petrol. London: Ashgate.

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