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Prevention Measures

IDENTIFYING THE SOURCE OF

LEAD POISONING IN EACH INDIVIDUAL CASE

Mr. Mike van Alphen

Introduction

To achieve population-wide reductions in child Pb exposure, there are strategic actions available at the national level and other levels of government. These actions may include removing Pb from petrol, introducing and implementing food safety and drinking water regulations, implementing regulation of the use of Pb in consumer products such as cosmetics, children’s toys, eating utensils, paints, and other goods. They may also include the regulation of particular industrial practices, waste generation, occupational health and the employment of children in hazardous industries.

These strategies are ‘the big picture’ that would bring about the ‘greatest good to the greatest number’. Similarly, the education of the public about Pb hazards is an attempt to reduce population-wide Pb exposure. In the meantime there are individual children who are Pb poisoned who require assistance.

Given limited resources, there must be a plan for allocating resources to the management of individual cases of Pb poisoning. While in the US for example, children with a blood lead level (PbB) of 10-20 m g/dl may get individual attention from the public health system, as they are a low proportion of the overall population. In a setting where the mean child PbB may be 10 to 20 m g/dl, while 10% of the population have PbB > 35 m g/dl, the country may have the resources to deal only with individual cases at PbB > 40-50 m g/dl.

The decision on how to allocate resources among the entire population, while giving special attention to individual cases, is a difficult one. However, this discussion assumes that there are some criteria in allocating resources to specific cases.

Individual Children, Specific Pb sources, and Exposure Reduction

To identify the sources of Pb exposure to an individual child can sometimes require knowledge of all of the locations that the child spends time in, the types of behaviors and activities of the child, and all of the possible relevant Pb sources. Even then, standard environmental testing for sources may not provide sufficient certainty about the sources of Pb and the best strategies to reduce Pb exposure in an individual child.

The ultimate aim of finding the sources of Pb exposure to a child is to strategically eliminate the sources of exposure and their pathways. Sometimes there will be one potent Pb source, sometimes many. One may have to come up with a defensible argument as to what particular Pb sources are the high priority sources to be eliminated for a particular child.

In highly contaminated settings adjacent to a suburban smelter, for example, children with normal hand-to-mouth behavior will have highly elevated blood lead (PbB) levels. The child’s home surroundings are highly contaminated, and will always be contaminated while the smelter operates, and potentially for long periods of time after the cessation of smelting. In this scenario, many aspects of the child’s environment, food, water, homegrown produce, house dusts, soil, water and air may combine to contribute to the Pb exposure of the child. Secondary intervention in the homes of these children may or may not be met with reductions in the child’s Pb exposure. In this situation the primary Pb source is the smelter and the focus has to include dealing with the smelter as a source. In some situations, consideration has to be given to removing families and children from close proximity of potent Pb emission sources.

At the other end of the spectrum is a home setting, almost devoid of obvious Pb contamination: there is no petrol Pb derived dusts, there has been no paint Pb disturbance, there are no Pb hobbies in the house, and no Pb industries nearby. Yet in this setting, an individual child can have high PbB while other siblings have very low PbB. This scenario now requires some focus on the daily routine, the geographic range of the child’s daily travels, the network of human contacts of the child, the behaviors and activities of that individual child. One may discover that the Pb source is a single source that may be easily eliminated, such as a painted chair or toy that the child chews on, or a favorite eating bowl that only that child uses and that happens to be Pb glazed.

Between the above two scenarios are the commonplace examples of child Pb exposure. Multiple children in a family could be exposed to a wide range of Pb sources, where it may not be possible to clearly identify the priority order of the Pb sources on first inspection. However there will be opportunities to reduce Pb exposure. However, one needs to remove the potential/probable Pb sources as soon as possible from the child’s home setting.

Where blood lead levels (PbB) exceed 40 m g/dl, it may be possible to readily discover key sources of Pb exposure by a routine home visit. It may be as obvious a condition as a Pb industry operating near the home. However, more detailed inspections may be required in most cases.

In the case of PbB between 20 and 40 m g /dl, one may require detailed knowledge of the daily routine of the child to guide one to finding the sources of Pb. Environmental testing may be essential to the discovery of where particular Pb hazards exist. For PbB < 15 -20 m g /dl it may take intensive behavior observation and knowledge of all the activities of the child and family and detailed environmental testing to determine the probable sources of Pb in a particular child’s home setting.

Blood Lead Levels of the Family and Other Clues to Possible Pb Sources

The pattern of PbB among occupants of the same home can frequently provide insights as to whether Pb poisoning is child-specific or just indicative of more widespread Pb exposure among siblings and adults. The PbB testing of siblings is the first priority. When you are struggling to discover a Pb source in the home, the testing of all home occupants can be useful. It is just one of many strategies. A number of hypothetical scenarios of PbB across a family are provided in Table 1.

1. Typical ‘take-home’ Pb poisoning with the male parent bringing home Pb

   contaminated dusts.

2. A home Pb contamination scenario, (nearby factory?) where the mother spends

   much of the day at home and the 6 year-old is at a distant school

3. There is a very specific Pb source affecting the 3-year-old child; for example, the

   child plays with a Pb painted toy or a Pb pigmented crayon or with a disused car

   battery case or sucks the art-paint off their paintbrush, or plays with a brass

   elephant.

4. The 6 year-old child delivers and shares lunch with his father. Or the father drinks

   moonshine whisky and the child has an unrelated Pb exposure.

5. The younger two children spend half a day at grandparents and drink limejuice from a tinned jug.
6. There is an indication of a universal Pb source in the home; perhaps the water supply or cooking-ware contains high levels of Pb.

Patterns of PbB among family members may provide some insights into the source of Pb exposure. However there may be many sources contributing to the exposure. Note how there is no data available for the 6 month-old child in Table 1; the youngest children and the unborn are at greatest risk and require consideration even if they may not have been tested.

The Exchange of Information

Good communication is the key to tracking down a source of Pb poisoning for individual children.

You cannot rule out the many possible idiosyncratic uses of Pb in the home and it is important that the home occupants can tell an investigator of all the potential Pb containing materials in the home setting. Education as to all the possible forms of Pb and uses of Pb, particularly through graphical means, is essential. If home occupants are not made aware of the many forms and sources of Pb, then Pb sources will be overlooked. Some relevant education will quickly be repaid when occupants in a home can subsequently point to the use of Pb containing items in and around the home.

For a child under 2 years, the Pb source is usually in the home, as this is where the child spends the vast proportion of his time. Exceptions are where mothers and fathers look after their infants while at work. Strategies like finding out where a child spends most of its time even inside and around the home are important with respect to tracking down localized sources of exposure. Older children may be Pb exposed at a number of locations.

Does the child:

• Usually visit a parent’s or relative’s workshop, e.g.: radiator repair, ceramic manufacture, battery manufacture, battery assembly, pigment manufacture
• receive childcare provided by grandparents, family members or others at another location
• live in other households for part of the week, holidays, weekends

Gather information on the daily routine, the geographic range of the child’s daily travels, the network of human contacts of the child, the behaviors and activities of that individual child. Somewhere there is a clue as to either the time of day, location, activity or associates with whom that child is Pb poisoned. At a first meeting you will gather a skeleton of these details. The next job is to try and eliminate or identify particular settings where a child may be exposed.

In discussing the Pb poisoning of a child, the history of the home and neighborhood can be an important factor in tracking down aspects of child PbB and household contamination:

• has the home previously been used as a factory
• has there been a factory nearby
• has soil from an industrial site been placed near the house
• has a child’s toy been painted with lead paint; can you find the paint-can used
• has any contaminating activity recently been carried out at home e.g., Pb melting/recycling, making fishing sinkers, breaking car batteries, reloading ammunition, has paint been recently disturbed in or around the house

In the case of children with pica you will need to ask about the range of non-food items that a child is known to eat. It is useful to know also about the non-food items that end up in the fecal matter of the child. Clues such as parts of toys, pieces of crayon, and flakes of paint have frequently been important evidence as to the range of potentially Pb contaminated materials ingested.

The collection of information may be made more systematic and in fact easier by referring to a checklist or questionnaire.

As soon as you are sure that you have identified a Pb source or sources, make sure that you provide practical and realistic advice and, if possible, the means for the elimination of that Pb source or sources. That advice should be sufficiently well considered that it does not pose any additional harm.

The Home Visit

Where blood lead levels are highly elevated you will want to conduct a home visit sooner rather than later. It is likely that the source of Pb exposure will be found in the home, particularly if children are less than 2 years old. Simple inspection may be all that is initially required.

An inspection of the home may be enough to identify probable sources such as a child’s toy made from Pb, a container of kohl, or a stack of car battery cases piled near the house. Where the child sleeps and plays, and where food is prepared, are important areas to look. Any part of the home setting where there is a workshop or hobbies or cottage industry carried out will also be worth inspection. Ask to see any stores of paints used recently around the house, cosmetics, tinned (Pb-Sn alloy) eating and cooking-ware.

The Pb analysis of strategic house dust, soil, paint, food, water and a range of items in a child’s surroundings may be a key to evaluating Pb sources and improving the knowledge base for further home Pb investigations.

Environmental Testing as a Means of Tracking Down Pb Sources

Where drinking water is tested, simple use of standards such as 10 m g /L can be used as an indicator of whether there is a major child Pb exposure problem. Similar guidance for other materials such as dust and soil as in Table 1 can be a guide as to whether these materials pose a low or high risk. However when assessing individual Pb poisoned children, one must be aware of additional site specific and case specific details.

In the case of Pb poisoning of young children, the first question that one may want to answer is ‘Is the Pb poisoning happening in the home?’ The dust Pb contamination of the home setting is the key measure that one might initially use to assess house-by-house contamination. In the case of Pb in soil and Pb in dusts, normal child hand-to-mouth and mouthing behavior can be sufficient to account for a large portion of a child’s Pb exposure.

However, in order to use a variable such as house dust Pb as an appropriate input for the acquisition and testing, house dust in the home settings of the community must be included. The statistical distribution of house dust Pb loading and/or Pb concentration results are used to evaluate the relative contamination of houses. What one needs is a method of acquiring samples that is relevant to large sectors of entire communities. Carpet dust samples are going to be irrelevant in poor communities living in huts having cement or earth floors. Collection of gentle floor sweeping of dusts may be most appropriate. It is the sample acquisition method that defines the distribution of Pb results obtained. This may not be the case for Pb in soil, Pb in drinking water, Pb in eating utensils and other matters.

Dust is the key source of Pb exposure of many children. Yet there may not be universal comparable measures of dust Pb accumulation in the home. The means of obtaining a measure of dust contamination that could be applied in earth floor huts as well as carpeted suburban houses would be the development of techniques for the measurement of dust Pb fallout in the home. Collections of dust Pb in devices such as petri dishes placed in uniform locations, as on platforms at above-door-height for example, could readily acquire dust Pb deposition rate measurements in one to four weeks, depending on the location.

Dust Pb loadings appear to dominate Pb exposure in urban settings where there is little exposed soil, and children spend most of their time indoors. In dry climates where there is a lack of surface vegetation such as grass, there can be large quantities of dusty soil material around and in houses, and on well-trafficked entryways to houses. Not only can children get frequent access to such soil in close proximity to the house, it is the dusty fraction of such material that can make its way into the house. Lead is tracked into the house via soil-dust in dry weather and via the tracking of soil-mud in wet weather. In poor communities and/or agricultural communities, there is the potential for a soil-dust continuum between the inside and outside of the home, requiring a fresh consideration of exposure assessment.

Child Pb exposure is not often as simple as one source of exposure; many of the child Pb exposure sources are interrelated, for example:

• air containing Pb will also be associated with the deposition of Pb
• floor Pb loadings are associated generally with Pb in air and Pb dust deposition rates and Pb in soils
• food containing Pb may or may not have been derived from contact with food containers; many food products are prepared with large quantities of drinking water

Environmental testing may focus on some key materials such as soil, and paint chips that a child has been known to eat. The key is to prioritize for testing purposes those areas where the most time is spent, and therefore, where the probability of exposure is greatest. Focus specifically on those Pb sources that the child does come in contact with. If a child plays for 2-3 hours a day on a mound of dirt and spends 10 minutes a day at another site playing in the soil, the former location must receive greater priority for testing if all other factors are equal.

When it comes to testing environmental samples it may be a luxury to be able to analyze soil, dust, paint, and water, but the experience gained from such testing can be employed to help the wider community.

As a rough or indicative guide only, without ever reverting to the word ‘safe’, values in Table 2 provide crude indications of the range of environmental measures of Pb and their implications. The indicative values of Table 2 readily provide clues about where child Pb exposure problems may occur, given a range of Pb concentrations and measures in environmental media. Do not interpret these values as if they are standards.

There are only a few orders of magnitude difference between ‘low’ blood lead levels, such as < ~ 1m g/dl and levels that are recognized to cause harm, e.g. > 10 m g/dl, and again those values that cause severe consequences, e.g. 100 m g/dl. Environmental Pb levels from ‘low’ to ‘high’ vary over narrow ranges, as seen in Table 2. There are only differences of orders of magnitude between environmental Pb values to which individuals are exposed that are likely to cause severe consequences and those that are causing only ‘minor’ levels of harm.

 

Table 2. A guide to the narrow band of Pb concentrations in environmental media that represent the transition from low Pb exposure to Pb poisoning.

 

Idiosyncratic Exposures or Pb Exposure from Consumer Products

In many countries the use of Pb in many types of consumer products is now either banned entirely or tightly regulated. In the developing countries this may not be the case, and there is a need to develop an acute awareness of the many and varied forms in which Pb will turn up.

Lead has many properties which permit it to be used in a wide range of applications. The list in Table 3 of items containing Pb is by no means exhaustive, and is likely to be substantially expanded just from the experience in India. One needs to be aware of the wide range of esoteric or idiosyncratic sources of Pb that regularly Pb poison children and adults alike.

The ease of recycling of materials containing Pb is an issue to be wary of. Painted timber, timber from a Pb mine, Pb from car sump-oil -- these when re-used as fuels cause inhalation exposure, and can directly contaminate food. Ash from a fireplace can become grossly contaminated and subsequently contaminate outdoor garden soils, plants, and so on. Another example from Bangalore is the use of refined Pb-rich sump oil as an oil-base for use in agricultural chemicals. An example from Australia is the use of Pb contaminated sump oil as a base for a timber fence-stain preparation.

Summary

Knowledge about all the possible sources of Pb, and the testing for Pb in products and environmental media such as deposited dusts, soil, water and many other materials, are essential to the discovery of Pb sources in the home setting of the individual child.

There are many different strategies for evaluating the sources of Pb poisoning in individual children; for guidance:

• focus on PbB testing to understand patterns and geographic distributions of individual exposure
• collect family and child network information that relates to the child’s activities and the locations where the child could be possibly exposed
• make sure that all people associated with a child’s well-being are able to understand all the possible Pb items that a child can come in contact with
• remove or otherwise deal with obvious sources of Pb exposure that can be quickly dealt with
• test those house dusts, soil materials, toys and eating utensils that children are actually or highly likely to be exposed where there is some doubt as to where lead exposures are derived
• provide follow up advice to families after testing, and wherever possible, offer practical assistance
• do no harm!

Finally, one must be aware that some well-meaning interventions directed towards lowering PbB have at times done the opposite.

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