Cadmium and lead accumulation in important food crops due to wastewater irrigation: Pollution index and health risks assessment

Abstract

The contamination of farm soils with heavy metals (HMs) has raised significant concerns due to the increased bioavailability and accumulation of HMs in agricultural food crops. To address this issue, a survey experiment was conducted in the suburbs of Multan and Faisalabad to investigate the spatial distribution, bioaccumulation, translocation, and health risks of cadmium (Cd) and lead (Pb) in agricultural crops. The results show a considerable concentration of Cd and Pb in soils irrigated with wastewater, even though these levels were below the permissible limits in water and soil matrices. The pollution index for Cd was mostly greater than 1 at the selected sites, indicating its accumulation in soil over time due to wastewater irrigation. Conversely, the pollution index for Pb was below 1 at all sites. Among the plants, Zea mays accumulated the highest concentration of Cd and Pb. The translocation factor from soil to root was highest for Brassica olearecea (7.037 for Cd) and Zea mays (6.383 for Pb). The target hazard quotient (THQ) value of Cd exceeded the non-carcinogenic limit for most vegetables. The highest value was found in Allium cepa (5.256) and the lowest in Allium sativum (0.040). In contrast, the THQ level of Pb was below the non-carcinogenic limit for most vegetables, except for Allium cepa (1.479), Solanum lycopersicum (1.367), and Solanum tuberosum (1.326). The study highlights that Allium cepa poses the highest health risk for humans, while Medicago sativa poses the highest risk for animals due to Cd and Pb contamination. These results underscore the urgent need for effective measures to mitigate the health risks associated with HM contamination in crops and soils.

Keywords: Allium cepa; Bioavailability; Health risks; Medicago sativa; Permissible limits; Target hazard quotient.

Fig. 1

(A) Pollution index values of Cd and Pb at selected wastewater irrigated sites, (B) Relative percentage of pollution index concerning level of contamination at wastewater irrigated sites.

Fig. 2

Translocation factor values of Cd (A) and Pb (B) in different vegetable and fodder crops at Multan. Bars indicate the mean values of the bioaccumulation factor and translocation factor (soil to roots, roots to shoot, and soil shoot) in different plants, and error bars show the standard deviation among the number of samples analyzed.

Fig. 3

Bioaccumulation and translocation of Pb (A) and Cd (B) from soil to root, root to shoot, and soil to shoot in different crops at Faisalabad. Bars indicate the mean values of the bioaccumulation factor and translocation factor (soil to roots, roots to shoot, and soil shoot) in different plants, and error bars show the standard deviation among the number of samples analyzed.

Fig. 4

Cd (a) and Pb (b) translocation model in different crops and person correlation analysis of Cd and Pb bioaccumulation, translocation factors (soil to root, root to shoot, and soil to shoot) in different crops (c). * Showing the p-value less than 0.05, ** showing the p-value is less than 0.01, and *** showing the p-value less than 0.001.

Fig. 5

Daily intake of Cd and Pb (A) and health quotient (B) of humans associated with consumption of contaminated vegetables. Daily intake of metals (C) and cumulative Cd and Pb health quotient (D) in cattle from consumption of contaminated fodders crops. Target hazard quotients for humans from consuming contaminated vegetables (E). In figures, bars indicate the mean values.