Methodology
Detailed Methodology and Methodological Limitations
Two sampling methods were used to test the toys and children's products found on the HealthyToys.org site.
Researchers selected toys and other children's products that represented the most common types of products used by US children. The products were purchased at chain stores including Target, Kmart, Toys R Us, Babies R Us, TJ Maxx, and Wal-Mart, as well as drug stores, dollar stores, and independent toy stores. Purchase locations included Ann Arbor and Ypsilanti, MI, Seattle, WA, Oakland, CA, Boston, MA, and New York, NY.
Researchers strove to select toys from a variety of "toy categories" as established by the toy industry. These categories are: action figures & collectibles, activity gyms & play mats, arts & crafts supplies, backpacks, bath toys, crib toys, feeding products, bibs, dolls, costumes, infant books, soft & plush toys, pacifiers, rattles & teethers, outdoor toys & sporting goods, preschool & interactive toys, shoes, trains & construction toys, and vending machine toys.
XRF Testing Methodology
Researchers tested products using a handheld x-ray fluorescence (XRF) device manufactured by Innov-X Systems(download XRF Factsheet). The XRF analyzer uses a technology known as x-ray fluorescence (XRF) spectrometry to detect certain chemical elements such as lead, cadmium, chlorine, arsenic, mercury, tin, and antimony.
The elemental composition of the materials reveals the presence of potentially dangerous chemicals such as heavy metals, and also allows researchers to infer the possible presence of toxic chemicals or materials, including brominated flame retardants (BFRs); polyvinyl chloride (PVC) and phthalate plasticizers. We have translated the research results into a HealthyToys.org toy rating system to allow users to easily compare the chemical levels of a variety of popular toys and children's products. There are a number of chemicals of concern that cannot be detected by this technology.
As several different organizations contributed data to this project, researchers conducted tests in several locations across the country. The exact XRF device protocol used by the organizations varied somewhat, but was based on the following general protocol. Before each testing session researchers calibrated the XRF machine using a known standard. Three calibration tests of 120 seconds were conducted and the results compared with the known levels. In all cases, results were within 25% of the known levels. Standard testing time was 30 seconds, with longer tests of 60 seconds or more conducted where elements of concern (other than chlorine) were detected.
Because the x-ray penetrates just a few microns deep (in metals) to 1/4 inch deep (in plastics and other softer substrates), the measurements should be considered surface measurement.
We interpreted the results using the concentrations and deviations reported by the analyzer, together with visual examination of the spectra generated by the instrument. The analyzer reports concentrations of elements by analyzing the spectra using reference data for the elements it reports, by measuring the area under the curve in the spectrum. We visually examined the spectra to confirm the presence of reported elements, and have not reported them where we could not confirm presence.
Methodological Limitations
The levels of lead, cadmium, chlorine, and other elements shown in this website are those reported by the XRF analyzer manufactured by Innov-X Systems, Inc. Our testing methodology uses standards with known levels of certain elements to check the accuracy of the analyzer in one type of matrix material. However, the toys and other products we tested are made of many different types of materials, in some cases even within the same product. These materials may interfere with the analyzer's ability to quantify the elements accurately. In addition, where the materials in a single product are not homogeneous, the test results may vary depending on the orientation between the object under test and the testing device. Where the testing is not able to isolate a single material, the reported levels may represent an averaging of the levels in the different materials. Interferences can occur between elements as well, such as with lead and arsenic, resulting in poorer precision. To the extent possible, we attempted to establish the degree of the interference.
Therefore, the levels we report provide a general indication of the levels in the products in order to guide consumers on product choices. More exhaustive testing with the XRF, as well as laboratory testing, could provide more detailed findings on the levels of elements and associated compounds.
Non-XRF Methodology
Some toys, children's products and jewelry were tested for lead levels using non-XRF technology. Toys and childrens' products tested with this methodology are noted in the database with the designation "digestion."
Detailed descriptions of the technologies used to determine lead content are described below.
Total Lead Analysis
Total lead analysis was performed to determine the amount of lead
present in an item or component of an item, such as a charm or pendant.
First, jewelry and component samples were collected and any coatings
present on the items were removed to be sampled separately. Care was
taken to prevent damaging the underlying metal and contaminating the
samples. Next, the samples were chemically digested (dissolved) in
nitric acid. Once the sample was completely dissolved, it was diluted
so that it could be accurately analyzed using atomic absorption
spectrophotometry (AAS). For every tenth sample, a duplicate was
created and tested to ensure accuracy (Weidenhamer & Clement, 2007).
Atomic Absorption Spectrophotometry (AAS)
Atomic absorption spectrophotometry is used to determine the elemental
composition or trace impurity of an item. This is a sensitive analysis
that is both accurate (the values reported are in line with the actual
values) and precise (actual values that are in close proximity to each
other give reported values that are in close proximity) (AAS, 2004).
Atomic Absorption Spectrophotometry (AAS). (2004). Retrieved November 5, 2007, from Northern Analytical Laboratory, Inc. Website: http://www.northernanalytical.com/tech4.htm
Weidenhamer, J.D. & Clement, M.L. (2007). Widespread lead contamination of imported low-cost jewelry in the US. Chemosphere, 67, 961-965.
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