Assessment of heavy metal residues in common vegetables from Colombo, Sri Lanka

Abstract

Vegetables are essential components of daily diets and contribute significantly to the nutritional needs of the Sri Lankan population. With increasing concern over environmental pollution and its potential impact on food safety, it is important to investigate even at a preliminary level the presence of heavy metal residues in commonly consumed produce. This investigation aimed to provide an initial insight into the levels of selected heavy metals; arsenic, cadmium, chromium, copper, lead, and nickel in carrots, leeks, and cabbage obtained from the Colombo district. The study was designed to serve as an early indicator of possible contamination trends and to emphasize the importance of routine surveillance. Fresh samples were collected from wholesale vendors in the Colombo Manning Market. In the first assay, 1 kg samples were analyzed to reflect common household consumption quantities, allowing practical assessment of potential daily intake levels. Heavy metal concentrations were analyzed using microwave digestion and inductively coupled plasma mass spectrometry (ICP-MS). The heavy metal analysis of Sample 1 showed cadmium at 0.15 mg/kg detected only in carrots. Copper was detected in all three vegetables: 0.64 mg/kg in carrots, 0.3 mg/kg in leeks, and 0.14 mg/kg in cabbage. Nickel was found at 0.3 mg/kg in leeks, remaining below the FDA/WHO maximum permissible limits. Arsenic, chromium, and lead were not detected in any samples. Among all metals screened, in Sample 2, only copper was present across all three vegetables, but its levels were well below the WHO/FDA safe limit of 73.3 mg/kg. The highest copper concentration was observed in carrots (0.36 mg/kg), followed by leeks (0.31 mg/kg) and cabbage (0.23 mg/kg). Although this investigation provides only a preliminary overview, the results indicate low levels of heavy metal contamination in the analyzed vegetables. These findings highlight the importance of ongoing monitoring efforts to safeguard food safety and promote sustainable agricultural practices, particularly within urban settings.