The results of this study suggest that aluminum and brass cookware readily available for purchase in the United States contains high lead levels and leaches sufficient lead to represent a potentially important source of lead exposure. This lead-containing cookware appears to be manufactured overseas, where it is imported to the US and distributed for sale both online and in traditional retail outlets.

The findings from this present study confirmed that traditional Afghan pressure cookers contain very high lead levels and leach sufficient lead to exceed childhood IRLs. All nine Afghan pressure cookers we have tested (i.e., six from our previous study and three in this current work) yielded sufficient lead to exceed both the adult and childhood IRLs. Although several of the Afghan pressure cookers tested in the previous study were hand-carried from Afghanistan and donated for analysis, the pressure cookers in this present study were purchased from online retailers in the United States. Even though two of the pressure cookers analyzed in the present study are a different brand from others tested, they exhibited similar lead content and lead leachate levels. This finding suggests that lead contamination is independent of manufacturer and reflects the widespread use of lead-contaminated scrap aluminum in Afghanistan.

Every hindalium item contained high lead levels and the amount extracted during the leachate tests exceeded IRLs. We evaluated these items because aluminum cookware has been identified as a potential source of lead exposure in India [23]. In addition, India is one of the world’s largest producers of aluminum [24], and Indian cookware made from aluminum is readily available for purchase in the United States.

Hindalium is the trade name for an alloy comprised of aluminum, magnesium, manganese, chromium, silicon, etc., and is produced in India by the Hindustan Aluminium Corporation (also known as Hindalco) [25]. However, marketing materials for hindalium cookware often use similar terms, such as “indolium,” “indalium,” and “hindolium.” Despite attempts at correspondence with Indian authors of relevant papers and other articles, we were unable to verify from metallurgists or other technical specialists whether these terms refer to the same alloy. However, email correspondence with Indian cookware vendors suggested that the terms are used synonymously. (Note that “indolium” typically refers to an unrelated cationic substance, also known as 1H-Indol-1-iumyl) [26].

As stated previously, we became aware of hindalium via a 1998 study conducted in India, which evaluated the leachability of lead from pressure cookers [20]. This study concluded that while pressure cookers introduced lead into food, their contribution relative to the lead content of the foodstuffs being prepared was relatively low. However, this study used tap water and tamarind juice for extraction, which are likely less acidic than the 4% acetic acid used in our experiments (the pHs of the extractants were not provided in the paper).

Another study from India investigated migration of aluminum from indalium cookware and concluded that these vessels contributed significantly to the total daily intake of aluminum through foods [27]. The concentrations of lead and other toxic metals were not measured. Interestingly, concern about aluminum from cookware as a cause of Alzheimer’s disease and other neurological conditions is very common on the internet, including on Indian web sites. One example, published by a member of an ashram, specifically cautions against using hindalium cookware because of aluminum extraction into foods [28].

All the brass cookware from India contained very high lead levels and/or the amount extracted during the leachate tests exceeded IRLs.

We discovered brass cookware in our search for hindalium items to purchase. In India, brass is an increasingly common cooking material, and many consider it to confer health benefits [29, 30]. Brass is primarily an alloy of copper and zinc, and lead is frequently added to improve corrosion resistance and machinability [31]. Some brasses can contain up to 7% lead [32]. However, as is the case with aluminum, lead levels can potentially be higher without treatment of source material or adequate quality control in the recycling process.

The stainless steel cookpot bodies contained very low lead levels and the amount extracted during the leachate tests did not exceed IRLs. However, all four stainless steel pressure cookers imported from India were fitted with a pressure relief vent pipe that contained high lead concentrations, with two exceeding 50,000 ppm. This finding is consistent with our previous study, where we speculated that vent pipes are comprised of brass or another lead-containing alloy. Nonetheless, no stainless steel cookpots yielded sufficient lead in leachate to exceed IRLs. The electric pressure cooker favored by the Afghan community as a safer alternative to lead-containing traditional pressure cookers (Pot #99) did not yield sufficient lead in the leachate test to exceed IRLs. However, a lead concentration of 87 ppm was detected in the vent pipe of this pressure cooker. Although vent pipes do not appear to contribute significant amounts of lead to the acetic acid solution, lead-containing components should not be used in cookware.

Figure 2 depicts the leachate results for all the cookware tested by our program, including cookware described in our previous study [1]. This complete dataset contains data for 96 individual pieces of cookware, manufactured primarily from aluminum (62 pieces), hindalium (7 pieces), brass (5 pieces), and stainless steel (22 pieces). This figure demonstrates that (1) no stainless steel cookware leached lead above levels of concern, even after 24 h; (2) for the other materials, significantly more lead was extracted after 24 h, compared to 15 min; and (3) leachate concentrations are typically significantly higher in hindalium and brass cookware than in other aluminum alloys.

Concentrations 15 min after simmering (15 min) are in white, whereas concentrations 24 h after sitting at room temperature (24 h) are in gray. The median concentration is depicted by the middle line; the lower and upper interquartile concentrations are depicted by the box, and the minimum and maximum concentrations are depicted by the lower and upper whiskers.

Our 2022 paper described the strengths and limitations of this type of study in detail, where strengths included the benefits of using an XRF analyzer to screen cookware. Evaluating our XRF analyzer’s response against a series of lead calibration standards in aluminum and stainless steel matrices ensured that the instrument was appropriately configured for this study. The importance of this practice was underscored when working with partners using different analyzer models, particularly when screening stainless steel items (their analyzers yielded false positive results). We found the following factors to be critical: (1) the measurement time must be of sufficient duration to reduce error and increase precision, (2) the appropriate calibration program must be used for the material being tested, (3) the analyzer responses against calibration standards should be critically evaluated, and (4) the spectra must be available for review – to evaluate the possibility of false positive results, especially near the instrument’s limit of detection.

Our development of a leachate test to estimate exposures that account both for cooking and storage of food in cookware was also a significant benefit of this study.

Limitations include the limited sample size of tested cookware, due to resource constraints. Consequently, while we can make generalizable statements about the hazards associated with preparing food in some aluminum, hindalium, and brass cookware, the extent to which other commonly available metallic cookware available in the United States marketplace represents a lead poisoning risk is unclear.

Our test method involved boiling the acetic acid for 15 min. However, we recently learned that the procedure employed by NSF International under its P390 standard (stovetop cookware for home use) involves simmering acetic acid for 30 min [33]. In addition, a recent recommendation from the FDA and a proposed certification from Clean Production Action specify simmering for 2 h [34, 35]. Consequently, our test method may extract less lead from cookware and therefore may be less health-protective than these other approaches. We also recognize that the degree to which lead is extracted from cookware is dependent on pH. However, it was beyond the scope of this present study to investigate the impact of using lower acetic acid concentrations, which may more accurately reflect the pH of many foods prepared in this cookware.

Our study did not examine the impact of cookware aging on extractable toxic metals. Surfaces that have become pitted or damaged with use could potentially release more lead. We also did not consider the potential contribution of lead from aluminum or brass utensils.

A significant uncertainty with our experimental design was the application of a leachate test to cookware that is typically used for frying or steaming foods at ambient pressures. Although we consider it inappropriate for any cookware to contain detectable levels of lead, a more representative approach for these items would be to measure the amount of lead extracted into heated edible oils or steam. However, relatively acidic sauces and other liquids may occasionally be added to the contents of frying vessels and then heated.

Finally, the assumption that both children and people of childbearing age consume 250 mL (i.e., 1 cup) per day from this type of cookware may under- or over-estimate their exposure.