Lead Levels in Spices From Market Basket and Home Lead Investigation Samples in North Carolina

Market Basket Survey Samples

An intern purchased 50 spice samples from 9 grocers in or near Raleigh, North Carolina, from August 23 through November 14, 2017. The local lead investigator advised the intern on what brands of spices to purchase for 9 product categories (adobo, asafoetida, chicken tikka masala, chili powder/red pepper, cinnamon, garam masala, tea, turmeric, and whole chili peppers). These target categories were types of spices and other products commonly consumed by families living in the area and often found by the local lead investigator to have elevated lead levels compared with other frequently sampled products. The lead investigator also advised the intern on sampling locations based on where local families reported buying their spices (5 national grocery store chains, 2 small specialty grocery store chains, and 2 independent local specialty grocers). The intern also purchased 3 other products (githeri masala, tandoori masala, and masala–no description) that were excluded from the target category analysis because they could not be matched with investigation samples.

Lead Investigation Samples

Certified lead risk assessors conducted lead investigations and took environmental samples in households of North Carolina children with confirmed elevated blood lead levels to identify the sources of lead exposure. A standard lead investigation in North Carolina consists of an interview with the family about suspected sources of lead and daily activities, lead poisoning prevention education, lead measurements by x-ray fluorescence machines, and sample collection from paint chips, dust wipes, drinking water, soil, and, when applicable, consumable products such as foods or herbal remedies. After the investigation, lead investigators enter or upload investigation reports, sample results, sketches, photographs, and notes into a property record in NCLEAD for surveillance and regulatory purposes.

We extracted environmental lead sample analysis results for spices and other consumable products (n = 689) from NCLEAD for 103 home lead investigations, conducted from February 1, 2011, through October 22, 2020. These samples included other food items outside the target categories, including other spices such as black pepper, cumin, and tamarind. We analyzed environmental sample data, with no link to identifiable information or related biospecimens; therefore, this study did not meet the definition of human research as defined by the National Institutes of Health.

Laboratory and Data Analysis

Using methods described in the 2005 Methods of Analysis of AOAC International, ¹² the North Carolina State Laboratory of Public Health incorporated dry ash into the sample, with stepwise heating to 450 °C to remove volatile organic materials, to increase the sample size up to 1 gram. The North Carolina State Laboratory of Public Health then digested the remaining ash material using hot block digestion following the National Institute of Occupational Safety and Health 7303/7082 measurement methods and quantitated the amount of lead by inductively coupled plasma optical emission spectrometry using the US Environmental Protection Agency (EPA) SW-846 6010D measurement method.^13-15 Samples with lead levels <15 mg/kg were further analyzed using an inductively coupled plasma mass spectrometer, referencing EPA Method 200.8. ¹⁶ Samples were excluded if the lead level was missing from the investigation report, the laboratory analysis method was different than the previously mentioned methods, or the product was grown in the family’s own garden rather than purchased in a store or mailed to the family. Data were analyzed using SAS version 9.4 (SAS Institute, Inc). Descriptive statistics were calculated to compare the distributions of sample results between sample types and by country of purchase. A Wilcoxon 2-sample median test was used to compare the difference between median lead levels by country of purchase and sample type, with α = .05 considered significant. Because of the exponential differences between the minimum and maximum sample results, the authors transformed the data using the natural log (log_e) to create the final data visualization on a graph in Tableau Software 2020.2 (Tableau Software, LLC).

Limitations

This study had several limitations. First, samples collected from lead investigations often had missing product labels, whereas the market basket samples were collected by study staff members who deliberately recorded the product origin information and retained the clearly labeled packaging. Therefore, purity could not be compared between product brands because of the small number of samples with product labels and large number of brands represented. Without clear product labeling, lead investigators also cannot report heavy metal contamination to the FDA or other regulatory agencies to trace the source and issue a recall. Unfortunately, product labeling for spices sold in the United States is inconsistent and does not always include information about where the products were grown and manufactured.

Second, insufficient data were available to estimate spice consumption rates or the contribution of lead from contaminated spices to children’s blood lead levels. In late 2018, NC CLPPP implemented the North Carolina Spice and Home Remedy Survey, a survey tool created for lead investigators to gather spice and home remedy consumption data and product information (Figure 2). Since NC CLPPP halted lead investigations during the COVID-19 pandemic and many families refused investigations that were offered, lead investigators have not had many opportunities to administer the survey to families. Still, NC CLPPP has evidence that lead-contaminated spices contributed, at least in part, to many children’s elevated blood lead levels. ¹ An analysis of these data could provide estimates of typical spice consumption rates among young children in North Carolina and better estimate the contribution of spices to elevated blood lead levels.

OPEN IN VIEWER

Figure 2.

A mother demonstrating for the lead investigator how much of each spice she uses in cooking. During lead investigations, getting product information can be challenging because families often do not have the packaging and do not remember where they purchased the products. Photo credit: Christen Klaus.

Third, whole spice samples were not collected as frequently as ground spice samples; as such, median lead levels could not be compared between the two forms of the same spices. Several studies have linked lead poisoning to repair of grinding machinery used for processing flour.^22-24 One turmeric sample included in the analysis, which contained 890 ppm of lead, was grown in India and ground by a relative who used a metal container and hammer to grind the turmeric before sending the spice to the family, who ate it for a year. By the time the source of lead was discovered, the child had a venous lead level of 15 µg/dL, which dropped to 9 µg/dL within 9 months after discontinuing consumption of the turmeric (NCLEAD, unpublished investigation report, 2011). For spices that consumers can purchase unprocessed, such as turmeric, chili peppers, and cinnamon, grinding the spices at home using a food-grade grinder may reduce a potential opportunity for heavy metal contamination.