your kale is full of metal
Kale and other brassica vegetables such as cabbage are exceptionally good at taking up thallium from soil. A 2006 peer-reviewed paper by Czech researchers confirms this to be true of kale,1 and a 2013 study from China found the same issue in green cabbage.2 In fact, brassicas are so effective at soaking up thallium that in 2015 Chinese researchers found they could use green cabbage to purify soil of thallium.3 In other words, the cabbage soaked up all the thallium in the soil, leaving the soil itself toxin-free. Think about that the next time someone offers you a kale smoothie or coleslaw made with conventionally grown cabbage!
J. Pavlíčková et al., “Uptake of Thallium from Artificially Contaminated Soils by Kale (Brassica oleracea L. var. acephala),” Plant, Soil and Environment 52, no. 12 (December 2006): 484–91, https://doi.org/10.17221/3545-PSE.
Yanlong Jia et al., “Thallium at the Interface of Soil and Green Cabbage (Brassica oleracea L. var. capitata L.): Soil-Plant Transfer and Influencing Factors,” Science of the Total Environment 450–51 (April 15, 2013): 140–47, https://doi.org/10.1016/j.scitotenv.2013.02.008.
Zenping Ning et al., “High Accumulation and Subcellular Distribution of Thallium in Green Cabbage (Brassica oleracea L. Var. Capitata L.),” International Journal of Phytoremediation 17, no. 11 (2015): 1097–104, https://doi.org/10.1080/15226514.2015.1045133.)