Ecological risk assessment of dieldrin presence in soil and vegetables: a case study in Indo-Gangetic region, Gaya, India

• Dieldrin contamination in soil samples is higher than in vegetable samples. • Green mustard was found to be highly contaminated with dieldrin. • Children & adults are most vulnerable to cancer risk via dermal exposure. • Moderate ecological risk was found in earthworms, rats, and birds. Contamination of dieldrin in soil and vegetables are reported even after its regulatory ban in many countries. However, monitoring of such persistent organic pollutants is not consistent in India. Still regional-level studies and report on dieldrin contamination are limited. Gaya Ji, being the 2 nd largest economic district of the 3 rd most populous state, Bihar, in India, is chosen for monitoring regional dieldrin contamination levels in soil and vegetable grown in the area. The present study monitored contamination of dieldrin in soil-vegetable samples to assess the health and ecological risk related to its exposure. 53 soil and vegetable samples were collected from Gaya district. Dieldrin was extracted with soxhlet extraction unit and estimated by Gas Chromatography Mass Spectrometry Detector (GCMSD). 2,4,5,6-tetrachloro-m-xylene (TCmX) was used as a surrogate standard, which yielded 71.94% - 89.91% recovery. Dieldrin concentration in soil and vegetable ranged from 0.04-1.33μg/g and 0.0019-0.97μg/g, respectively. 95.75% of the contaminated soil samples showed higher concentration than limit set by the Dutch Serious Risk Concentration (SRC) in 1976. 93.75% of vegetable samples showed contamination above the MRLs set by EU/WHO in 1994. Human risk assessment indicated that children (5-11 years) and adults (≥20 years) were the most vulnerable to cancer risk due to dieldrin exposure via dermal route. Adults and toddlers (7 months- 4 years) were the most vulnerable to the non-cancerous risk due to dieldrin exposure via ingestion route. Ecological risk assessment carried for earthworms, rats, and birds based on their modeled toxicity values given by Agriculture & Environment Research Unit (AERU) at the University of Hertfordshire, UK in 2016. The assessment indicated moderate risk for 47.82% soil and 12.5% vegetable samples. The findings of the present research reveal serious contamination and risks related to dieldrin exposure. Thus, demands regular monitoring and remediation studies to reduce its persistence in the environment.