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Environment & Product Monitoring

LEAD IN PAINTS AND WATER IN INDIA

Mike van Alphen

Introduction

Lead exposure in India is a complex matter which is only beginning to be understood. Some of the sources and pathways such as small scale Pb industries, traditional medicines and cosmetics, tinned (Pb-Sn alloy) eating utensils, Pb in drinking water supplies and Pb in milk products - are just some of the many issues that require specific evaluation in India. While child Pb poisoning attributable to Pb in paint is commonplace in certain other countries, paint may not account for a high proportion of child Pb poisonings in India.

However, 10% of Pb metal consumed in India is said to be used in the manufacture of paint, and wherever such paint is used there will be the potential for human Pb exposure. By comparison, some 11% of Pb consumed in Australia in the early 1970’s went into pigment and chemical production (Roberts, 1977). While the use of dry powders and other ‘white-wash’ type non-Pb-based paints are perhaps widespread, and many homes in India are without painted interior surfaces, the question remains; where does the Pb consumed in paint manufacture in India end up? What proportion of Pb-based paints manufactured in India make their way into residential settings or into contact with children?

If white-lead pigment material is finding its way into products like icecream in India, it would be no surprise to find white-lead in paints in India. Should there have been widespread use of white-lead pigment in India, there would be a clear cause for concern with respect to paint being a source of child Pb poisoning. As a preliminary measure it was decided to carry out a small survey of commercially available paints.

Selection of Paint Samples

Immediately after the Bangalore conference conducted by The George Foundation, a selection of 24 paint samples from six paint companies were purchased in stores in Bangalore and Chennai (Figure 1). Paint in the can was taken back to Adelaide, Australia for analysis. None of the paints selected had any warnings on the labels as to the Pb content or any guidance as to what uses of the paint may or may not be hazardous. One of the indicators as to the possible Pb content of the colourful timber paints in India was the limited range of colours available. Most paint companies offered the same range of colours, using the same paint names. Many of these colours were characteristic of the mineral compounds that make up the lead-chromate group of pigments.

A selection of five white paints and timber primers were purchased with a view to potentially discovering white lead. Apart from a metal primer, the remaining paints were bright, colourful enamels for timber surfaces in blue, green, red, orange and yellow that might be readily used on children’s toys. This was not a representative selection of paints; they were readily available in cans from 50-100 mls to 4 litres capacity. These types of paints or at least the colour range represented by these paints are commonly seen on temples and shrines in Bangalore and Chennai.

Six Australian paints including 3 lead-chromate paints were prepared along with the paints collected in India. These materials had been analysed in detail previously and were used as a check on the analysis process. In addition, one white lead and one red lead paint were used in trials for the development of the sodium rhodizonate test used here.

Figure 1:

A selection of some of the paints purchased in Bangalore and Chennai in

February 1999 and tested here. Eleven of the 24 paints tested and some of the products shown here contained less than 1% Pb by weight.

Analysis

The paint was evaluated using three analytical techniques: portable X-ray fluorescence (XRF), wavelength dispersive electron microprobe analysis (EPMA) and a low cost qualitative test using sodium rhodizonate.

The paints purchased were applied to a wide range of substrates; for the analyses presented here, two coats of paint were brushed onto areas of at least 30 x 50 mm on timber blocks. A separate new brush was used for each sample. Tongue-depressor sticks (used to stir the paint in the can) were the substrate for the qualitative spot tests.

XRF

A Niton XRF, using a Cd¹⁰⁹ source, energy dispersive detector and a 60 second analysis (based on PbL) was used for the analysis of the painted timber blocks (Figure 2) (Niton,1999). Tests were carried out a week after the paints had been first applied. Thirty analyses were conducted in a little over half an hour.

Electron Microscopy

Four timber-plus-paint chips for each sample were removed from adjacent to the spot analysed by XRF and mounted in 25 mm diameter araldite blocks, sectioned and polished using 1 micron diamonds. Analysis was conducted in a Cameca SX51 electron microprobe having 4 wavelength-dispersive spectrometers. The micro-analysis was performed on two of the four mounted paint chips at 5000x magnification rastered over an area of 15.4 x 23.3 microns, using a beam current of 20 nA and accelerating voltage of 15 kV. Quantitative EPMA for Pb was conducted over 20 seconds and analysis for 11 other elements conducted over 10 seconds each on the appropriate spectrometer. In addition an energy dispersive spectra with a resolution of 140eV was acquired for each sample to qualitatively assess the elements present in the samples. Sixty analyses were conducted over a six hour period.

Sodium Rhodizonate

Paint lead tests using this reagent are widely used; however the method required some adaptation so as to deal with lead chromate pigments. Commercial test kits using this method only claim to identify ‘leachable lead’ and may for example take 18 hours to conduct the test. The tests were carried out by first placing a filter soaked in an NaOH solution onto the paint so as to etch the paint. This was particularly necessary so as to analyse the freshly painted, hard and somewhat corrosion-resistant lead chromate paints. This was carried out using 10g NaOH per 100mls of distilled water. For most samples this etching results in a rapid colour change of the paint and contact is only required for two minutes. Any further contact with the NaOH soaked filter would resemble a paint-stripping process and not etching. In the case of white lead or red lead the NaOH etch stage is unlikely to be required. Four hard and glossy paints, all products of the one paint company, were resistant to this attempted etching even after 30 minutes. More work is required on developing a pre-treatment method; however these problems may only be present in new unweathered paints. Some ‘hi-tech’ pigment particles are armoured with silicates and are resistant to acid / alkalai attack. Lead chromate pigment with such particle armouring is likely to be of very low immediate Pb toxicity.

The paint is allowed to dry after the NaOH soaked filter is removed, and the paint is placed in contact with a new filter soaked in tartaric acid solution at 10g per 100mls. When this filter is dry, it is ‘developed’ using a spray bottle of freshly prepared sodium rhodizonate solution at 0.1g per 100mls of distilled water. For lead based paints, such as white and red lead, the filter will turn bright scarlet red wherever it was in contact with the paint. For lead chromate paints the filter will turn scarlet red more particularly in those regions etched by the NaOH.

The method described here is not a field testing method and is highly destructive of the paint surface, but can be modified to be used less destructively, safely and reliably in the field. The sodium rhodizonate method was used on surfaces that had been painted three weeks previously. The 30 samples tested, including six Australian paints, took only 30 minutes over a period of an hour due to long drying times in cool humid weather. This process would have been faster in warmer conditions.

Figure 2 Painted timber sample blocks: the bright colours are typical of Indian timber paints and lead chromate pigments. A central area of the blocks was analysed by XRF. Four chips of timber and paint were removed for electron microprobe analysis.

Results

The XRF results are expressed as a lead loading as milligrams of Pb per square centimetre, based on a two coat paint thickness on a surface area of ~ 5 mm x 10 mm. The electron microprobe results are reported as weight percent Pb based on the average of two analyses over an analysis area of 15.4 x 23.3 microns. The sodium rhodizonate analysis records the presence or absence of Pb near the paint surface (in this case over a filter area of up to 7 cm diameter).

Of the 24 samples analysed (Table 1):

• 17 had Pb concentrations exceeding 0.5% Pb by weight
• 13 had Pb concentrations exceeding 1% Pb
• 5 exceeded 10% Pb

On the basis of a two coat paint thickness, the XRF determination of paint Pb loading exceeded 1 mg/cm² on five of the samples. The lower Pb concentration paints are the white, blue and brown-red paints, while in order of increasing Pb concentrations are the green, red, orange and the yellow paints.

Table 1.

Samples in order of increasing Wt % Pb	Weight % Pb	Pb (mg/cm2)	Low cost qualitative	Paint Color
	(WD-EPMA)	FP XRF	Sodium Rhodizonate
1	<0.1	<0.1	- ve	ultra white
2	<0.1	<0.1	- ve	white primer
3	<0.1	<0.1	- ve	white
4	0.1	<0.1	- ve	brown red
5	0.2	<0.1	- ve	white
6	0.3	<0.1	- ve	phiroza
7	0.3	<0.1	- ve	oxford blue
8	0.5	0.1	- ve	phorozi
9	0.5	0.1	- ve	brown red
10	0.6	0.1	- ve	oxford blue
11	0.6	0.1	- ve	brilliant white
12	1.6	0.2	+ ve ?	signal red
13	3.2	0.4	+ ve	bus green
14	4.0	0.5	+ ve	new bus green
15	5.0	0.8	+ ve	deep green
16	6.0	0.9	+ ve	post office red
17	6.1	0.8	*- ve	mint green
18	6.2	0.4	+ ve	post office red
19	7.8	0.6	*- ve	signal red
20	11.4	2.0	*- ve	tractor orange
21	13.0	1.9	+ ve	tractor orange
22	16.8	2.8	*- ve	golden yellow
23	17.7	2.0	+ ve	golden yellow
24	20.2	3.8	+ ve	golden yellow

* these newly applied paints were unaffected by NaOH in 30 min. More evaluation required.

The presence of Cr and S in association with the Pb, as well as the colours of these paints as already indicated, strongly indicate the presence of lead-chromate pigments (van Alphen, 1998). Given the availability of alternative pigments, the question arises as to whether a very high percentage if not all golden yellow, tractor orange and bus green etc, colours in India contain Pb. To what extent do we need chemical testing of paints? While indications are that blue paints are not commonly Pb rich, there is an industrial sublimed blue lead pigment to watch out for!

The sodium rhodizonate method failed as a screening test for some of these freshly applied paints as 4 samples having Pb concentrations over 6% returned false negative results. However none of those four hard and glossy lead-chromate bearing paints showed any etching by either the NaOH or tartaric acid solutions. Some further development of a low cost spot test method is warranted. This method readily identifies white-lead or red-lead paints. Clearly more samples need to be tested and a more robust method developed so as to quickly and cheaply identify paint Pb routinely. For old and weathered lead-chromate paint surfaces, this method may be useful as it is.

The applicability of low cost qualitative tests for paint Pb in India require further discussion. The essential costs may be as low as 2-10 Rupees per test whereas commercially available sodium rhodizonate test kits can sell for the equivalent of 200 Rupees each in Australia. It is possible to test some 30 or more paint surfaces per hour in the field using this method. Meantime more method development may be required and questions related to the adequacy of a 1-2% Pb method detection limit should be addressed.

Conclusions

Thirteen of the 24 selected Indian paint samples tested had Pb concentrations exceeding 1% by weight. There will be problems of child Pb poisoning in India attributable to Pb in paint. The Pb in the paints collected were dominated by a group of pigments best described generically as lead-chromates. Weathered lead-chromate paints are likely to be toxic when ingested and have been eliminated from sale for residential purposes in many countries since the 1960’s and 1970’s.

The commercial availability of the Pb pigmented paints analysed in this survey indicate that there is limited regulation of Pb in paint in India. While white-lead and red-lead paint products were not readily available to be purchased in this very brief survey, more information as to the presence or absence of these very Pb rich paints is required. If lead-chromate paints are readily available, perhaps other pigments are also available commercially for one reason / purpose or other. These pigments include:

• white lead Pb(OH)₂.2PbCO₃
• red lead Pb₃O₄
• basic sulphate of lead 2PbSO₄.PbO
• calcium plumbate Ca₂PbO₄
• lead titanate PbTiO₃

There appears to be no regulation as to labelling on paint cans containing Pb in India. Consumers would have no awareness of the Pb content of paints, or the unsuitability of such paints for many purposes. There is likely to be a reservoir of painted objects in residential settings in India that are accessible to children which pose a Pb exposure risk. The extent of child Pb exposure attributable to such paint is unknown, but it will not be trivial. The history of use of white-lead and red-lead pigmented paints among others and the extent of residential use of various paints requires investigation in order to begin to adequately evaluate the risks posed by paint in India. There is an immediate high-priority need to ensure that these colourful Pb pigmented lead-chromate paints are not applied to children’s toys.

The next clear priority is in relation to the highly toxic white-lead pigment. If white-lead is still manufactured it is recommended that the Indian Government should consider that it be comprehensively banned from any form of manufacture under the appropriate ‘poisons regulations’.

Thereafter there is a need to quickly assess what regulations are more generally required in the areas of paint labelling, paint manufacture and ‘poisons regulation’. There is a need for a comprehensive survey of the paint manufacture industry in India to establish the patterns of manufacture of Pb paints and determine whether there are opportunities for diversification into alternative manufacturing processes.

Finally, while there is the lead in paint issue to be addressed in India, there are many other high priority sources and pathways of Pb exposure to be assessed. While in the US, for example, Pb in paint is a key source of child Pb exposure, it is unlikely that this is the case at the present time in India.

SUGGESTIONS FOR A STRATEGIC NATIONAL SURVEY FOR LEAD IN DRINKING WATER

The low pH, soft water conditions that are responsible for the leaching of Pb from water pipes is essentially determined by the interaction of rock and soil with rainwater and surface water infiltrating into groundwater. It is the geology that imparts the characteristics of the water, which in turn determines the chemical aggressiveness of water in contact with brass, lead, and solder in water pipes, and hence, Pb in drinking water. Of course if there were no Pb in pipes there would not be a problem; however that is so invariably not the case. It is therefore possible to exploit the very predictable nature of the geology of India as has already been well surveyed at regional scales, to predict where highest Pb-risk water supplies occur.

Using both geology and water quality parameters, it will be possible to prioritize a national strategic evaluation of Pb in water resources in India. What is required is a matching of water quality data (Pb, pH and softness) and regional scale geological maps that define the chemistry of surface and ground water reservoirs.

Data and tasks are:

1. Collate existing drinking water (end of tap) Pb values and pH and hardness values

2. Make associations between low water pH, soft water and elevated Pb content in end-of-tap water and data on the underlying geology of source-water reservoirs

3. Where the geology determines water characteristics of low pH and soft water and high Pb dissolved in the water from pipes, predictive models for Pb in water are refined in an iterative process

4. Geographic information systems or simple mapping studies, utilizing water well data, water catchment data, geological data, population data and political boundaries can be used to prioritize evaluations of Pb in drinking water over large areas of the country

It may well be that some granite or high-grade metamorphic areas have Pb leaching problems whereas areas underlain by sedimentary limestone or marble will be less impacted by lead leaching from water supply and delivery pipes. The use of geographic information systems that integrate population data, political and catchment boundaries and geological data with the water-based data on a national scale would provide a quick and powerful tool for the assessment and management of this problem.

Still at the strategic level are issues of design and materials in pumping equipment, piping in individual wells, water distribution and household systems. The presence of lead-jointed mains pipes, brass, and lead solder in components of these systems will be an issue if there are systemic regional differences. A survey of water quality and Pb in water on a national or regional scale may be able to address multiple public health issues without substantial additional resources if well coordinated with public health authorities and laboratories.

References

Niton (1999) X-ray fluorescence analysers http://www.niton.com/xrf.html (seen 29 March 1999)

The George Foundation (1999) Conference Agenda and Notes Lead Poisoning: International conference on Prevention and Treatment, Hotel Ashok, Bangalore, February 8-10 1999.

Roberts, P.J. (1977) Lead. in Australian Mineral Industry 1975 Review. Australian Government Publishing Service. Canberra.

van Alphen, M., (1998) Paint film components. National Environmental Health Forum, General Series Number 2. South Australian Health Commission, Adelaide.

Acknowledgements

Thanks are due to Huw Rosser for his assistance with electron microprobe analyses and to John Terlet at the Centre for Electron Microscopy and Microanalysis of South Australia for making the Cameca SX51 facilities available. X-ray fluorescence analyses were kindly provided free by Jason Bawden-Smith at JBS Environmental Pty Sydney.

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