Measurement of Heavy Metals in Commercially Available Soybean and Palm Oils and Relevant Health Risk Assessment in Bangladesh

Abstract

Background: Soybean and palm oils are widely consumed in Bangladesh.

Objective: The study aimed to investigate the levels of heavy metals and estimate their health risks in nationally representative samples of branded and unbranded soybean and palm oils sold in retail stores in Bangladesh.

Methods: A total of 1,521 soybean and palm oil samples were collected from eight administrative divisions. National composites of branded oil were prepared by combining at least 12 samples for each brand. In the case of unbranded oil, composites were prepared for each administrative division. A total of 44 composite samples, including 23 soybean oil samples (19 branded and 4 unbranded) and 21 palm oil samples (13 branded and 8 unbranded), were tested. Twenty-five individual samples (11 crude and 14 refined) collected from the refineries were also analyzed to trace the origin of the heavy metals. Market samples were analyzed for arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb) and only mercury (Hg) in both market and refinery samples using various atomic absorption spectrophotometric techniques. The possible adverse health effects of exposure to heavy metals content in edible oil were estimated using the tools of daily exposure ( $D_E$ ) and noncarcinogenic risk assessment hazard quotient (HQ).

Results: The median values of As, Cd, Cr, Pb, and Hg content in soybean and palm oil respectively ranged between $6.9\text{and}8.8\mu g/\mathrm{kg}\left(\mathrm{As}\right)$ , $4.3\text{and}6.9\mu g/\mathrm{kg}\left(\mathrm{Cd}\right)$ , $12.3\text{and}42.3\mu g/\mathrm{kg}\left(\mathrm{Cr}\right)$ , $19.4\text{and}27.8\mu g/\mathrm{kg}\left(\mathrm{Pb}\right)$ , and $1.73\text{and}5.11\mathrm{mg}/\mathrm{kg}\left(\mathrm{Hg}\right)$ . The differences in heavy metal contents between branded and unbranded oils were not statistically significant. Except for Hg, all other metal concentrations were within national and international standard limits. The estimated $D_E$ of Hg through edible oil represented a considerable risk for noncarcinogenic health effects ( $\text{HQ}>1$ ). The ranking orders of HQ for the oil samples were as follows: unbranded soybean oil (3.99) > branded soybean oil (3.50) > branded palm oil (2.61) > unbranded palm oil (1.69).

Discussion: The present study evaluated the level of heavy metal contamination in soybean and palm oils and conducted risk assessments associated with their consumption in Bangladesh. It appears that the source of this contamination is the imported crude oil. Strong and effective monitoring infrastructure is needed to regulate the import of safe crude oils for refineries. https://doi.org/10.1289/JHP1072.

Figure 1.

Map showing the districts ($n=23$) from where edible oil samples were collected. This map was generated by plotting GPS points of the data and sample collections spots in a map of Bangladesh [R software (R version 4.1; R Development Core Team)]. The map was obtained from an open source and no permission is required. Note: GPS, global positioning system.

Figure 2.

Heavy metal concentration (Cd, Pb, As, Cr) in edible oil (market sample). Whiskers represent range, box limits represent the interquartile range (IQR), and midline of the box is the median. Note: As, arsenic; Cd, cadmium; Cr, chromium; Pb, lead.

Figure 3.

Mercury concentration in edible oil samples: (A) market sample, (B) refinery sample. Whiskers represent range, box limits represent the interquartile range (IQR), and midline of the box is the median.

Figure 4.

Hg in the analyzed composite market oil samples exceeding the Bangladesh Standard and Testing Institute (BSTI) level. *The BSTI limit for total Hg ($0.25\text{\hspace{0.17em}ppm}$); therefore, “within BSTI limit” represents the number of samples having Hg levels $<0.25\text{\hspace{0.17em}ppm}$. Note: Hg, mercury.