Portable lead analyzer to locate source of lead

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OBJECTIVE: To investigate the sources of lead in the environment in children with elevated blood, with the help of a Field Portable X-Ray Fluorescence Analyzer.
METHODS: One hundred and seven school children were chosen for this study on a random basis, from Mangalore and Karnataka. Their blood lead was analyzed. Of the cases analyzed, 10 students whose blood lead level was more than 40 µg/dl were investigated using a field portable X-Ray Fluorescence Analyzer. This is the first time such a device has been available for this purpose in India.
RESULTS: The 'likely' source of lead exposure could be determined in eight cases which was from the immediate environment of the children like 'lead-based' paint on surfaces in the house, on playground and other exterior equipment; lead storage batteries, contaminated dust and soil and other lead-containing substances.
CONCLUSION: The use of an X-Ray Fluorescence Analyser appeared to be useful in determining the source of lead.


Lead is the most common metal involved in chronic poisoning. It was one of the first metals known to man and has been widely used during the last two thousand years for domestic, industrial and for alleged therapeutic purposes. Lead is abundant in soil, being distributed throughout the earth's crust. Several of its salts occur as variously colored powders or liquids and are extensively used in industry, and at home, which can result in cumulative toxicity through chronic exposure and can even result in acute exposure. It has been used in lead storage batteries, therapeutics (lead acetate), paints (lead carbonate), glazing of pottery (lead oxide) and in petrol (tetra ethyl lead). Among cosmetics, lead tetroxide is the most common compound in vermilion (“sindoor”) applied by married Hindu women to the parting of their scalp hair, while lead sulphide is used as collyrium (“surma”) for the eyes by Muslims. [1] Lead chromate, a pigment used in yellow paint, is still widely used in India and elsewhere.
Field Portable X-Ray Fluorescence Analyzers (XRF) have been used for many years in the United States to determine the lead levels of painted surfaces. [2] A major advantage of these direct reading instruments, in addition to their ease of use and relatively low cost on a per sample basis, is that results are immediately available and feedback regarding potential health hazards can be provided to the family at the time of the home visit. These instruments have also been shown to produce results comparable to laboratory analysis for soil samples with a minimum of soil preparation and for air samples with no additional preparation. [3], [4] A method for the determination of lead in air by field portable XRF has been established by the US National Institute for Occupational Safety and Health. [5] Field Portable XRF instruments have also been found to be useful for the determination of the lead level of dust wipes collected from surfaces in housing. c Health-based standards for lead levels in paint, soil and dust wipes have been established. [7]
Debate continues over the nature, magnitude and persistence of the adverse effects on human health of low level exposure to environmental lead. However, the accumulated epidemiological evidence indicates that such exposure in early childhood causes a discernible deficit in cognitive development during the immediately ensuing childhood years. [8], [9],[10], [11] It used to be thought that neuro­psychological manifestations disappeared or declined if the ingestion of lead has stopped or reduced. [12] Recent data however show that such effects are largely irreversible. For blood lead levels <25 mg/dl (micro grams/deci litre) it appears that the size of the effect on the IQ, as assessed at 3years of age and above, is probably 1-3 points for each 10 µg/dl increment in blood lead level, with no definite evidence of a threshold [13], [14] As per some studies done in India, approximately 51% of children tested had levels >10 mg/dl, and 13% had values >20 mg/dl. The proportion of children with levels >10 mg/dl ranged from 40% in Bangalore to 62% in Mumbai. [15]

Materials and Methods
One hundred and seven school children were chosen for this study on a random basis, from 3 schools located in Mangalore, Dakshina Kannada district, Karnataka. They were selected after obtaining informed consent from their parents. There was an equal distribution from the point of view of socio-economic status among the children chosen for the study. A few drops of capillary blood were drawn using a sterilized lancet. Each sample was analyzed at the National Referral Centre for Lead Poisoning in India, Bangalore, by experts, using 3010B ESA Lead Analyzer which works on the principle of Anodic Stripping Voltametry (ASV). ASV is a CDC approved technique with a potential to analyze up to 200 µg/dl blood lead levels. It has been compared with Atomic Absorption Spectrophotometry. The finger stick procedure for collecting blood samples is an acceptable method as long as proper precautions are taken to prevent contamination and has been used in large-scale research projects in the US. [16] The National Referral Centre for Lead Poisoning at St. John's Medical College, Bangalore checks quality control, using these check kits. Of the cases analyzed, 10 of the 11 students whose blood lead level was more than 40 µg/dl were investigated by a team consisting of an environmental and industrial hygiene engineer, two environmental consultants, a biochemist, and a toxicologist. The investigation involved interviewing the concerned student and his/her teacher and parents, to explore possible sources of exposure, and determining the lead content of various painted surfaces in/near the housing and the concentration of lead in substances in the child's environment using a Field Portable X-ray Fluorescence Analyzer (XRF) manufactured by the NITON Corporation ( Billerica, MA, USA) on loan for demonstration purposes to one of the co-authors from the University of Cincinnati, USA. The model used was XL-309 with a Cd-109 source.
The team visited the students' school, play areas, and homes, and analyzed possible sources of exposure with the help of the XRF instrument, capable of estimating the level of lead (in units of mg lead per sq cm )on any surface on which it is placed. In this manner, the lead levels of painted surfaces such as windows, floors, gates, doors, door frames, walls, shelves, containers, cupboards, playground equipment etc., were determined. The other surfaces and materials tested included the floor tiles, kitchen platform, grinding stone, utensils used, the rice and spices ( masalas ) used, batteries, medicines taken, the soil outside the house, etc. The unit of analysis for bulk materials such as soil and powders is ppm . A dust wipe of the room in which the student normally slept was also analyzed and has units of µg of lead per sq. ft.
The NITON XRF Analyzer is also very effective in testing surface lead dust levels (with the use of dust wipes), soil (either in situ or after sieving), air samples and bulk dust samples. [4] [6] Field studies have confirmed the accuracy and cost effectiveness of using this for in-field dust wipe analysis. Studies have demonstrated excellent correlation between NITON results and laboratory Atomic Absorption Spectrometry. [3]Soil samples collected were later sieved and analyzed, along with the dust wipes, by graduate students in the Masters in Industrial Hygiene program at the Sardar Patel University (Gujarat) under the direction of two of the co-authors.

Results
The results of the blood lead testing of the 107 children studied were: 11 of the students had a blood lead level of >40 µg/dl, 8 of whom attended a government school in which students from low economic status study; the remaining 3 from this group were from another school and they belonged to affluent families. None of the other children had blood levels of 40 ug/dl or higher. One school out of the 3 chosen for the present study had no children exhibiting >40µg/dl of lead.
An attempt was made by the team to investigate the possible source or sources of these high lead levels, with the help of NITON XRF Analyzer. As a first step the team inspected the government school from which the large number of students with high blood lead levels were reported. The other school, where three of the children with elevated blood lead attended, was not visited. After determining that the possible sources in the government school were below the levels defined as “positive” for lead (US EPA 2001) [7]the team proceeded to the house of one of those students (A) with a blood lead level of 72.7µg/dl. There was no evidence of lead in and around the house. His mother said that he spent most of his free time in a nearby park. In the park, the team found the sea saw, swings, slide, jungle gym, etc., painted in bright colours which were peeling off. Yellow colour paint gave a maximum reading of 3.5 mg/cm2 while the orange colour was associated with a reading of 2.4 mg/cm2 of lead. A composite sample of the soil contained only a relatively low level of lead of 119 ppm (parts per million). [It was later learnt that the new soil had recently been placed in the area near the play equipment.] Municipal officials were later advised of the high lead paint and they agreed to remove it carefully and paint the equipment with lead-free paint. A follow-up blood sample three weeks after the environmental engineer visit revealed that the lead level had dropped (49.5 µg/dl), but was still elevated.
The next student (B) investigated was a boy with a blood lead level of 41.9 µg/dl. The team identified as a possible source of lead-containing yellow paint that had been applied to a railing at the rice mill where the child's family housing was located. No other sources were identified- painted surfaces in the family's room tested negative for lead (< 1.0 mg/sq cm).
The team then proceeded to the house of another student (C) whose blood lead level was 48.3µg/dl (and subsequently was 26.7 µg/dl when tested three weeks after the environmental engineer visit) and one more student (D) whose blood lead level was 60.6 µg/dl. All the results were negative for lead in both the instances except that a floor dust wipe taken at the home of child D contained 25.4 µg/sq ft; this level being lower than the current US standard for floors, 40 µg/sq ft, but does indicate a degree of contamination.
All the above students belonged to poor families. The team then decided to inspect the house of one student (E) from the other school, who had a blood lead level of 68.8 µg/dl. The parents of the boy were educated at the university level and were financially well off. After obtaining negative findings on analyzing the soil, dust, and paint, the parents were questioned extensively about the boy's food habits, hobbies, spare time, medications taken, etc. The parents recalled that while renovating their house 6 months earlier, they continued to live in other areas of the house, the boy used to open the paint tins and play with the paint. He had also been taking some folk medicines. One such medicine which did not have any label on the container, consisted of black coloured tablets, was analyzed. The tablets were crushed in the bag and analyzed while in the bag using the NITON XRF Analyzer. The results showed a value of 636+/-260 ppm. (The readings on the XRF were taken for what is known as “60 source seconds” which is the time recommended by the manufacturer. Longer readings would give more precise results). Later testing in a laboratory revealed a concentration of 850 ppm lead and an even higher level of mercury. The daily intake of lead from this source was about 1900 mg; the family was advised to discontinue taking this substance. The blood lead was 28 µg/dl, when tested about three weeks later, which supports the medicine being a major source of the lead for this child.
The next student (F) the team met was one who had been losing interest in studies. His blood lead level was 50.8µg/dl. His father worked as a gas welder, while his mother rolled beedies. The house was painted in different colours. The red colour paint on the door frame indicated a value of 3.2 mg/cm2, and the window bars which were painted yellow had a maximum value of 4.6 mg/cm2 of lead. On questioning the parents it was found that this child had the habit of licking the paint off walls (pica). The child frequently played with a friend in a nearby house under construction that contained metal scaffolding painted with a lead-containing yellow paint. Dust wipes were below the detection limit of about 8 µg/sq ft. The child's blood lead was slightly higher three weeks later, 54.2 µg/dl indicating that the exposure was continuing.
The team then visited the houses of two girls (G&H), both from the private school, whose lead levels were 60.2µg/dl and 91 µg/dl respectively. But in spite of all the analysis and the interview with the people at home, it was not possible to find out the source of exposure for child G (who lived above a spices ( masala ) factory); for child H, a lead storage battery in the home may have been a source of exposure. The family was advised to remove the battery; a follow-up blood test three weeks later revealed a marked drop in blood lead to 20.7 µg/dl suggesting that the battery may well have been a source of exposure.
Next the team visited the house of a 11 year old girl (I) from the government school, whose father complained that she had been losing weight and had not been doing well in the school. Her blood lead level was 58µg/dl. Negative values for lead were found on all the surfaces examined. From the history it transpired that as a child she used to spend time with her grandfather when he repaired fishing nets, using lead sinkers. On further interrogation, the father of this child revealed that they had an old dry battery in their house and she used to play with it. She had the habit of opening the battery case and licking the contents. The family was requested to remove the battery; a blood lead sample three weeks later showed a very large drop to 13.6 µg/dl, suggesting that the battery may have been an exposure source.
The last house the team visited was that of a 13 year old girl J from the same government school with a blood lead level of 52.9µg/dl. She was good at studies, did not complain of any sickness, and did not have a history of pica. All the suspected sources of lead demonstrated negative value. When the soil behind her house was analyzed, it gave a value of 59.2+/-37.0 ppm in the bulk screening and was later found to contain 377 ppm as a prepared sample, a definite sign of contamination since the lead level was much above the background levels of less than about 50 ppm. The XRF reading of 59.2+/-37.0 ppm corresponded to the reading of 56.3 in the atomic absorption laboratory at the University of Cincinnati.
The soil sample was collected from an area near a former tyre retreading and printing factory behind her house. Right in front of her house was a small tulsi katte (a plant around which an altar has been made for prayer). This altar had been painted with bright colours. The team found the orange colour to give a reading of 2.3 mg/cm2 of lead. These same paints were said to be used on occasion in body painting. A summary of environmental surveys of each of these homes is presented in [Table - 1] .

Discussion

In the present study, among 10 students with significant blood lead levels, efforts to determine the source of exposure were successful in varying degrees in 8 cases. In the case of the boy A studied, it is likely that the lead in his blood was from the brightly coloured swings etc., painted with lead based paint in an area where he routinely played. Child B lived at a factory where the only apparent source of lead was the railing near truck scales that was coated with lead-based yellow paint. F had the habit of licking the paint off the painted surfaces (pica), leading to ingestion of lead because there were many areas in his environment where lead-based paint had been used.
Many houses in this part of the country are still having numerous surfaces coated with lead based paint. The tulasi katti in front of J's house had considerable amount of lead. In child J, the culprit could be the factory behind the house as the soil showed high concentrations of lead. In child I, the lack of awareness about the danger of mouthing the contents of a battery could have led to the increase in blood lead level. It is possible that this child had obtained an exposure to lead since childhood as she used to play with the fishing net, which used lead in weights. For another child H, when the lead storage battery in the house was removed, there was a marked decrease in the lead level in a follow-up blood sample.
The present study indicates that while lead is a significant contaminant of the environment of children belonging to lower socio-economic groups, it seems to have spread its tentacles to the upper income levels of society also, though the number of children affected is less. The relevant exposure information that the team could obtain from the visit to the house of E was his hobby of playing with paint and the family residing in the house during its renovation, and his intake of medicines with considerably high content of lead.
Many earlier studies have concluded that a the decline in the academic performance of children in some cases could be attributed to lead exposure, and the anecdotal information obtained in this study appears to support those findings.
The use of a Field Portable XRF instrument has been shown to be an effective device, when combined with thorough observations and questioning, to help identify sources of lead in the environments of children with elevated blood lead level. The XRF can be taken to the site and the samples can be analyzed on the spot. The results are immediately available, it is easy to use and its cost effectiveness makes it an extremely efficient instrument for determining environmental contamination. Since the results are comparable to laboratory analysis, it is reliable also. Elsewhere in India the Field Portable XRF Analyzer has been used to show that many currently available new paints still contain high amounts of lead.[17] Future studies could use the XRF instrument's air lead determination features as well as an analytical method to measure lead levels in drinking water.

Conclusion
This study undertaken with the intention of determining the impact of environmental factors on blood lead levels of school children involved a new approach: the use of a Field Portable X-ray Fluorescence (XRF) Analyzer. No such study has been conducted in this part of the world so far. It is unique in many respects since a Portable XRF Analyzer had been used. This instrument led the investigating team to possible sources of exposure with quantitative data to support their findings. The advantages of the XRF are as follows:
1. The XRF can be easily used for 'onsite testing.' Large numbers of areas can be tested thus within a short time of one hour or two. In the case of other instruments like the AAS, the samples have to be brought to the laboratory for later analysis. The time required for sample delivery and analysis is usually at least a couple of days and can often be a matter of weeks.
2. A key and important feature of the NITON XRF analysis procedure is that it is non-destructive. For example in dust wipe samples, the XRF procedure does not alter the sample which can later be sent for confirmatory laboratory analysis of the same sample. Similarly the protocols for paint and bulk samples are also non-destructive and those samples can also be later analyzed by laboratory methods for confirmatory analyses if desired.
3. A third advantage is that several types of samples can be analyzed such as: paint, soil, dust wipes, bulk dust, other bulk materials and air.
4. Although not used in the field in this study, many of the XRF analyzers used are capable of analyzing simultaneously for a number of other elements such as arsenic and cadmium.
Such instruments are needed on a routine basis in lead poisoning control efforts.
Lead exposure is clearly a global public health issue, but it is only just being recognized as a potential problem in many developing countries including India. Efforts should be made to create public awareness about the precautionary measures to be taken to prevent lead poisoning as lead has shown to affect the performance of children. It must be made mandatory that paint should be unleaded, the soil near factories be decontaminated frequently, and folk medications rendered lead free.

Acknowledgement
Appreciation is expressed to the NITON Corp. of Billerica, Massachusetts (USA) for use of the XL-309 Portable X-Ray Fluorescence Analyzer. We are grateful to the District Administration and the Karnataka Pollution Control Board, Mangalore, for sponsoring the blood lead estimation of the children. This work would not have been possible without the Anodic Stripping Voltameter (ASV), at St. John's Medical College, Bangalore. Our thanks to the George Foundation, Bangalore, for installing this instrument and to the students of the Masters in Industrial Hygiene program at Sardar Patel University (Gujarat) for processing and analyzing the soil, dust wipes and other bulk samples. 

References
1. Pillay VV. MKR Krishnan Handbook of Forensic Medicine and Toxicology. 12th edn. Hyderabad, Paras Publication, 2001; 322-327
2. US HUD. Guidelines for the Evaluation and Control of Lead-Based Paint Hazards in Housing. U.S. Department of Housing and Urban Development, Office of Lead-Based Paint Abatement and Poisoning Prevention, Washington DC; 1995
3. Clark S, Menrath W, Chen M, Roda S, Succop P. Use of a Field Portable X- Ray Fluorescence Analyzer to Determine the Concentration of lead and other Metals in Soil Samples. Ann Agric Environ Med 1999; 6 : 27-32.
4. Morley JC, Clark CS, Deddens JA, Ashley K, Roda S. Evaluation of a Portable X-Ray Fluorescent Instrument for the Determination of Lead in Workplace Air Samples. Applied Occup Environ Hygiene 1999; 14 : 306-316
5. NIOSH. Lead by Field Portable XRF, Method 7702. Manual of Analytical Methods, 4th edn. National Institute for Occupational Safety and Health; 1999
6. Sterling DA, Lewis RD, Luke DA, Shadel BN. A Portable X-Ray Fluorescence Instrument for Analyzing Dust Wipe Samples for Lead: Evaluation with Field Samples. Environmental Research Series A 2000; 83 : 174-179
7. United States Environmental Protection Agency 2001, 40 CFR Part 745, Lead: Identification of Dangerous Levels of Lead; Federal Register: 2001; 66(4) : 1206-1240
8. Tong S. Lead exposure and cognitive development: persistence and a dynamic pattern. J Pediatr Child Health 1998; 34 : 114-118
9. Davis MJ. Risk assessment of the developmental neurotoxicity of lead. Neurotoxicology 1990; 11 : 285-292
10. Pocock SJ, Smith M, Baghurst PA. Environmental lead and children's intelligence: a systematic review of the epidemiological evidence. British Medical Journal 1994; 309 : 1189-1197
11. Schwartz J. Low level lead exposure and children's IQ: a meta analysis and search for a threshold. Environmental Research 1994; 65 : 42-55. 
12. Ruff HA, Bijur PE, Markowitz M, Ma Y, Rosen JF. Declining blood lead levels and cognitive changes in moderately lead poisoned children. J American Medical Association 1993; 269 : 1641-1646
13. Needleman H, Schell A, Bellinger D, Leviton A, Allred EN. The long term effects of exposure to low doses of lead in childhood: an 11 year follow up study. New England J Medicine 1990; 322 : 83-88
14. Tong S, Baghurst PA, Sawyer MG, Burns J, Mcmichael AJ. Declining blood lead levels and changes in cognitive function during childhood: the Port Pirie Cohort Study. J American Medical Association 1998; 280 : 1915-1919
15. George Foundation. Project lead-free: a study of lead poisoning in major Indian cities. In Proceedings of the International Conference on Lead Poisoning, Bangalore, India, 8-10 February 1999. Bangalore. The George Foundation 1999; 79-86
16. Galke W, Clark S, Wilson J et al. Evaluation of the HUD Lead Hazard Control Grant Program: Early Overall Findings, Environmental Research 2001; 86 : 149-156
17. Clark S, Sinha S, Nayak N, Menezes G, Dave P, Clark R. Levels in Lead in Soil and Paint in Karnataka and Gujarat (India), Proc. of Sixth International Conference on Environmental Contamination in Center and Eastern Europe and the Commonwealth of Independent States, Prague, Czeck Republic, Florida State University, Sept 1-4, 2003

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