Drinking Water QualityLead

Andrew HaddockMathew Nkem Ikediashi

1

Outline

Introduction. Occurrence in drinking-water. Toxic/Adverse effects. Rationale for water quality standard.

Case study. Methods of management.

2

Introduction Lead is the most common of the heavy metals, making up 0.0013% of the

earth’s crust.

It has been used in paints and pigments, in batteries, alloys, solder, pipes, ammunition, glazes, it was also used as an antiknock compound in petrol, however this has been phased out (WHO, 2003).

Lead has been known to be toxic for centuries, in the last 35 years experiments have revealed that it has health implications even at low doses.

As a result of the ban on the sale of leaded petrol in the UK in the year 2000 the levels of particulate lead in the environment have been reduced.

Levels in drinking water remain predominantly unchanged and can now provide the largest controllable source of lead intake.

(Gray, 2008).

3

How does lead get into drinking water?

Lead can enter water by leaching from◦ Lead-containing pipes◦ Brass faucets and Solder

The problem arises where water is plumbosolvent.

The rate of leaching increases dramatically below pH 8.0.

Other factors include the water temperature, the contact time between the water and the source of lead and the amount of lead piping

Vibrations in pipes, scouring by high water velocities, thermal expansion effects, age and nature of pipe, the presence of particulate lead deposits and electrochemical reactions caused by mixing pipes.

4

Occurrence in UK Drinking Water

Percentage of Households

Lead Concentrations in daytime

Sample (µg 1-1)England Scotland Wales Total

0-9 66.0 46.4 70.5 64.4

10-50 26.2 19.2 20.7 25.3

51-100 5.2 13.4 6.5 6.0

101-300 2.2 16.0 1.5 3.4

≥301 0.4 5.0 0.8 0.9

Total 100 100 100 100

5

Table 1. Lead concentrations in households in the UK during a survey in 1975-1976 by the Department of Environment. Reproduced from Gray, (2008).

Toxic/Adverse effects of exposure -Humans A wide variety of toxic and adverse health effects are

associated with the consumption of lead:

Neurological problems: significant impact on child development.

Hypertension and cardiovascular problems. Interferes with enzymes involved in haeme

synthesis resulting in anaemia. Disturbed calcium metabolism, bone/tooth

formation. Reduced Cytochrome P450 levels, reduction in drug

metabolizing enzymes. Reproductive abnormalities: depressed sperm

counts. Renal damage and abnormalities.

(WHO, 2003, WHO, 2008, Lanphear et al., 2000)

6

Toxic/Adverse effects of exposure -Animals

7

Research has found many adverse and toxic effects of lead on a variety of animal species :

Neurological problems in young primates at levels of 10.9 -33µg/dl which persisted into adulthood (Rice, 1987).

Studies of rats, mice and hamsters have shown that lead is carcinogenic in these species, causing predominantly renal tumours (Silbergeld et al., 2000)

Exposure of rats prepubertally to lead acetate in drinking water resulted in a reduction in testis weight in males and a disrupted oestrogen cycle in females (Ronis et al., 1996).

The current WHO guideline value of 0.01mg/l is derived from the Tolerable Daily Intake approach.

In 1986 Joint FAO/WHO Expert Committee on Food Additives set tolerable weekly intake at 25µg/kg bodyweight.

This is 3.5µg/kg bodyweight per day.

Based on child metabolic studies which suggested consumption of 3-4µg/kg bodyweight did not result in an increasing body burden.

Assumption being that 5kg bottle fed baby consumed 0.75l of drinking water per day.

(WHO, 2003, Gray, 2008) 8

Rationale for water quality standard-WHO.

Rationale for water quality standard-European Community.

The EC responded with the revised drinking water directive, lowering the maximum level to 0.01mg/l.

Costly work would need to be undertaken by member states to achieve this goal.

A fifteen year transition period was granted requiring member states to reach an interim value of 0.025mg/l by 25th December 2003.

The European interim standard will be tightened to 0.01mg/l in 2013 for all member states.

(Gray, 2008)

9

Case study: Washington USA

Potentially 42,000 children in Washington DC were potentially exposed to unsafe levels of lead in their drinking between 2001-2004 .

This was caused by a change in disinfectant in water treatment (from free chlorine to chloramine) in 2000. This change increased the plumbosolvency of the water, causing the corrosion and leaching of lead from piping.

In 2002 and 2003, the incidence of elevated blood lead (>10µg/dL) levels among children was greater than 4 times higher than in 2000 before the change in disinfectant.

Elevated blood lead levels were highly correlated with elevated water lead levels.

There were differences in the risk of elevated blood lead levels between neighbourhoods, areas with the highest number of lead pipes being high risk.

(Edwards et al., 2008)

10

11

Case study: Washington USA

Methods of management Alert consumers of the presence of lead in drinking water

– particularly those in high risk groups.

Reducing the plumbosolvency of water at treatment plants before discharge.

Avoid the use of substances in drinking water that make water more plumbosolvent (eg. Washington case study).

Line lead pipes, particularly service pipes.

Replace lead pipes entirely – best option but expensive.

(Gray, 2008)

12

References

13

Chen, A. M., Dietrich, K. N., Ware, J. H., Radcliffe, J. and Rogan, W. J. (2005) 'IQ and blood lead from 2 to 7 years of age: Are the effects in older children the residual of high blood lead concentrations in 2-year-olds?', Environmental Health Perspectives, 113(5), 597-601.

Chu, P. H., Lin, J. L. and Tan, D. T. (2005) 'The blood lead level in chronic hypertension patients', Journal of Hypertension, 23, S391-S392.

Dye, B. A., Hirsch, R. and Brody, D. J. (2002) 'The relationship between blood lead levels and periodontal bone loss in the United States, 1988-1994', Environmental Health Perspectives, 110(10), 997-1002.

Edwards, M., Triantafyllidou, S. and Best, D. (2009) 'Elevated Blood Lead in Young Children Due to Lead-Contaminated Drinking Water: Washington, DC, 2001-2004', Environmental Science & Technology, 43(5), 1618-1623.

Fulton, M., Raab, G., Thomson, G., Laxen, D., Hunter, R. and Hepburn, W. (1987) 'Influence of blood lead on the ability and attainment of children in Edinburgh Scotland', Lancet, 10(8544), 1221-1226. 

Gray, N. F. (2008) Drinking Water Quality, Problems and Solutions., Second Edition ed., United States of America, New York.: Cambridge University Press.

References Lanphear, B. P., Dietrich, K., Auinger, P. and Cox, C. (2000)

'Cognitive deficits associated with blood lead concentrations < 10 mu g/dL in US children and adolescents', Public Health Reports, 115(6), 521-529.

Rice, D. C. (1987) 'Primate Research - Relevance to human learning and development', Developmental Pharmacology and Therapeutics, 10(5), 314-327.

Ronis, M. J. J., Badger, T. M., Shema, S. J., Roberson, P. K. and Shaikh, F. (1996) 'Reproductive toxicity and growth effects in rats exposed to lead at different periods during development', Toxicology and Applied Pharmacology, 136(2), 361-371.

Silbergeld, E. K., Waalkes, M. and Rice, J. M. (2000) 'Lead as a carcinogen: Experimental evidence and mechanisms of action', American Journal of Industrial Medicine, 38(3), 316-323.

WHO (2003) 'Lead in Drinking-Water. Background document for preparation of WHO Guidelines for Drinking-water quality.' (Online)

http://www.who.int/water_sanitation_health/dwq/chemicals/lead.pdf (Available 10/03/11) 

WHO(2008) ‘Guide to drinking water quality’(Online) http://www.who.int/water_sanitation_health/dwq/gdwq3rev/en/

(Available 10/03/11)

14