Suggestions made regarding choosing testing methods for 7 material classes of possibly lead containing objects.

By Zac Gethin-Damon with advice from Martin Bagnall, Sampling Technologies Pty Ltd and Lance Smith, Sydney Analytical Laboratories.

There are three different things you may be looking at when you are testing an object:

1. the presence of lead over or between certain thresholds
2. the actual amount of lead in the object.
3. the migrational properties of lead in object: i.e. the degree to which the lead in the object can migrate into the bloodstream or other systems: soil, rainwater tank etc.

While tests which determine 1 and 2 are useful as rapid methods to identify lead it is the results of 3 which are the most useful to you: it is this amount which equates to the lead contamination potential of an object. Although an object may be composed of high amounts of lead, if the lead cannot leach out into the environment then it is harmless. However if no lead is present it an object it will obviously have no leach potential therefore tests which show 1 and 2 should be seen as useful in the way they indicate the need to test for 3.

We have identified 6 main tests which are available to you to test an object:

1. Lead Inspector Rapid Swab Test: Swab test which indicates the presence of lead by changing colour. The colour chart provided with the kit notes 5 possible colour changes, from beige: 1-3ppm lead to black: 50ppm lead.
2. 4 Hrs Leach Method: Comes with the Lead Inspector kit. Vinegar: a mild acid, is applied to the object and left for 4 hours to allow the lead to dissolve. The solution is tested after 4 hours against the same colour chart as in a).
3. Lead Check Swab Test Swab test which indicates the presence of >0.5% or 5000 parts per million (ppm) lead by changing to pink.
4. XRF RoHS Test (ppm): X-Ray Fluorescence is a rapid means of detecting the presence of lead and other heavy metals in paints, soils, metals, wood and other materials. XRF measures the total amount of the element (in parts per million or %) present by placing the test item onto the end of a hand held XRF instrument. Within 30 seconds, XRF will allow you determine if, a. Lead and other heavy elements are present. b. Determine if the concentration amount is high, medium or low level, and c. determine if you need to do further investigation with laboratory analysis.
5. Lab acid leach tests: As in b) but done under lab conditions and with stronger acids. The leaches were done with approximately a ratio of 20:1, i.e. f the object weighed 20gms, it was leached it in 400mL of acid. Initially 4% Acetic Acid, was added, the readings were then taken (i), then Nitric Acid was added to a level of 4% before taking the second reading (ii) A lot more lead will come out in the Nitric Acid as it is much stronger.
   

1. 4% Acetic Acid Leach (ppm Lead in solution):
2. 4% Nitric Acid Leach (ppm Lead in solution)

Let us separate them according to their purpose:

1. Tests which identify the presence of lead between and/or over certain thresholds:

a) Lead Inspector Rapid Swab Test: Min reading: 1-3ppm, max reading:>50ppm.

b) Lead Check Swab Test: >.5% lead.

2. Tests which identify the actual amount of lead in the object:

    c) XRF: In parts per million (ppm): an estimate.

   3. Tests which identify the migrational properties of the lead in an object:

     d) 4 Hrs Leach Method: As in a), min reading: 1-3ppm, max reading: >50ppm.

      e) Lab Acid leach tests.

The tests are often misleading.

The problem facing you as the person who wants to test an object for one of these things is that the validity of each of the tests will vary according to the material that the object you are testing is composed of.

What we did:

We have tested various items and arranged them according to the material they are primarily made from in order to determine which testing methods are appropriate for which materials.

How did we determine the appropriateness of each testing method?

To confirm the appropriateness of each testing method we look for agreement between testing methods across samples. Agreement means that the results do not contradict each other. For example if we take two items to be tested, lets say 1 and 2, and both testing methods a) and b) find 1 to be more leaded then 2, then these testing methods agree. Similarly where no lead is found by a) or b) the testing methods can be seen to agree. Where there is agreement between testing methods the validity of each test is suggested, oppositely where testing methods don’t agree the validity of either one of the testing methods is challenged. The testing methods have been arranged in terms of validity from left to right, with the lab acid leach tests e) being the most valid. Hence if a testing method is contradicted by a testing method on its right then its validity is challenged.

Substances Tested:

1. Paint
2. Metal
3. Ceramic
4. Teeth
5. Spice
6. Plastic

 Results:

1) Paint

c) The swab test indicated lead present in both cases.

d) The XRF test in the Kitchen Paint example suggests the Wall Paint is more leaded, yet the leach tests e) i. and ii. suggest that it is the Ceiling Paint which is the more leaded sample. As we are to take the leach tests as the more valid, this would suggest that the XRF result is not reflective of the true lead content of the paint. According to the company which did the XRF testing this could be for one of two reasons:

1. The paint sample may have had multiple layers of paint which varied according to lead content. As XRF tests all the layers of the paint and takes an average of the lead content the result does not always reflect the actual lead content of the item tested. If one layer of paint were leaded and one lead free for example, the lead-free layer would dilute the result and make it appear less leaded. 2. The other possibility is that a calibration error yielded an incorrect response. The example should be tested again with XRF.

Now the total lead in the sample must be more than 20 times the leached amount (e), because the ratio is 20:1. If you take the paint samples as an example, the Nitric acid leach for the wall paint is 460ppm. The total lead must therefore be greater than 20x460 = 9200ppm.

Allowing for experimental error the figure of 8000 from the XRF is close enough.

For the Ceiling paint, the nitric acid leach is 2380ppm. The total therefore must be greater than 20x2380 = 47600ppm. The XRF result of 5000 is incorrect. It could be that the XRF result is out by a factor of 10, which may have been just a calculation error.

Conclusions: What should I use to test paint?

1. To test for the presence of lead: c) Lead Check Swab Test will indicate when paint contains over 0.5% lead.

2. To estimate the amount of lead: d) XRF testing, while not indicative of the actual amount of lead in this case did indicate high amounts of lead. XRF testing is useful to identify if an object has low, medium, or high amounts of lead but further lab testing is required to confirm the actual lead content or migrational properties of an object.

3. To test for the migrational properties: e) Acid leach testing.

 2) Metal

1. The Lead Inspector rapid swab test cannot be used effectively on metal items. Those items that were tested and where a change in colour was observed:
2. the Chinese Scarf and the Enviroweights Bean were later shown to have minimal amounts of lead.
3. The 4 hour leach test is suggested to be similarly useless through the results, while indicating lead present in items shown by further testing to have lead, it also indicated the presence of higher amounts of lead in substances which later showed to have very minute amount, therefore disqualifying any results as valid.

b. The Lead Swab test in the metal example yielded effective results, in both cases where a pink colour change was observed, high levels of lead were found by testing methods d), e) and f)

d+e) The agreement between testing methods d) and e) suggests that XRF is useful to determine the amount of lead.

*We tested enviroweights as they claim to be a lead safe product. The very low lead results confirm this claim; we can recommend envirowieghts as a non-lead alternative to generic fishing sinkers such as the Metal Ball Sinker tested.

Conclusions: What should I use to test metal?

1. To test for the presence of lead: c) Lead Check Swab Test
2. To estimate the amount of lead: d) XRF testing
3. To test for the migrational properties: e) Acid leach testing

3) Ceramic  

1.  A comparison of the results would suggest that The Lead Inspector Rapid Swab Test only detected lead where there was at least more than 1.4 mg/kg (according to teste) ii.
2. The 4 hour leach test on the other hand showed no change in a test which was later shown by testing method e) ii. to be more leaded then 2 other examples were a colour change in the 4 hour leach test was observed: a false negative. This would suggest that the 4 hour leaching method is not a useful testing method for teeth.
3. The Lead Check swab test showed no lead in any of the four tested teeth. This is     most likely due to the limitations of the range of detection in this testing method.
4. The XRF tests showed there was no lead in the teeth while the leaching test e) ii. Suggested that there was lead in the teeth. This could be either due to the limitations of the range of detection or specific to this material: teeth. Either way the suggestion made through these results is that XRF is not a useful method for identifying small amounts of lead in teeth.

Conclusions: What should I use to test teeth?

1. To test for the presence of lead: b) At least >1.4 mg/kg

3. To test for the migrational properties: e) Acid leach testing.

5) Spice:

 a-c) Due to the yellow coloured nature of the turmeric tested, a colour change test was not practical.

d+e) The agreement between these three more exact tests would suggest that any of the three is appropriate for testing spices for lead. Clearly a more extensive test of spices would be required in order to draw conclusions.

Plastic  

 The low amount of lead indicated in both the examples in the three more exact tests makes it unclear if swab tests are useful or not. What is suggested in these results is at least small amounts of lead identified in testing methods e) cannot be identified in plastic substances through swab a+c), 4 hour leaching (b), or XRF (d) testing methods. A more extensive test of plastics would be required in order to draw conclusions.

To sum it all up:

While tests a) through to d) can be useful to quickly identify the presence of lead in an object/estimate the amount of lead in an object, any confirmation of the actual danger that an object may have requires laboratory acid leach testing e). What this document has tried to achieve is a demonstration of which tests are useful for identifying and/or estimating the presence of lead in different materials.