This study investigated nitrate concentrations and associated health risks in four commonly consumed vegetables in Iran. A total of 282 samples of cucumber, tomato, onion, and potato were randomly collected from markets across Khuzestan Province, and analyzed. Fresh vegetables were washed, homogenized, extracted, and analyzed using an optimized zinc-reduction Griess reaction-based spectrophotometric method (λmax = 537 nm) validated against high-performance liquid chromatography (HPLC). The highest levels of nitrate were observed in potato (87.107 ± 32.270 mg/kg) and cucumber (80.366 ± 30.099 mg/kg). Non-carcinogenic risk assessment showed target hazard quotients (THQ) and hazard index (HI) well below 1.0 for both adults and children. Lifetime carcinogenic risk (CR) exceeded the conservative 1 × 10−⁶ threshold only for cucumber in adults and for cucumber, potato, and tomato in children. The total carcinogenic risk (TCR) was unacceptable. These findings suggest that, despite acceptable non-carcinogenic risk, long-term consumption of these vegetables may pose an unacceptable carcinogenic risk, particularly to children. Regular monitoring of nitrate levels in vegetables and other dietary sources (e.g., water and processed meat) is therefore recommended. However, some reducing agents in vegetables and our body can convert nitrate to the more toxic metabolite nitrite. Therefore, factors such as dietary composition and individual physiological responses to nitrate warrant further investigation to refine risk assessments.
Pakravan et al. (Wed,) studied this question.