Summary
This study assessed heavy metal contamination in food crops (yam, cassava, cocoyam, waterleaf) harvested from the Ibaa community in Rivers State, Nigeria, an area adjacent to oil and gas pipeline infrastructure in the Niger Delta. A total of 48 samples (12 each of four crop types) were collected from the Ibaa community (crude oil-impacted Right-of-Way zone) and from a control site. Concentrations in Right-of-Way crops were significantly higher than control samples for all metals. Principal component analysis indicated two dominant contamination sources: lead and cadmium from petroleum activities, and copper from agrochemical use. EDI was highest in children, with maximum values for zinc (7.9 × 10^-1 mg/kg per day), copper (1.0 × 10^-1 mg/kg per day), and arsenic (9.5 × 10^-5 mg/kg per day) in cocoyam. Total lifetime cancer risk (TLCR) for arsenic reached 1.5 × 10^-5, exceeding the USEPA acceptable limit of 1 × 10^-6.
Key numbers
| Measure | Value | Units | Matrix | Source location |
|---|---|---|---|---|
| Mean lead (Pb) range (ROW crops) | 0.0028 to 0.0118 | mg/kg | Yam, cassava, cocoyam, waterleaf | Abstract |
| Mean arsenic (As) range (ROW crops) | 0.0002 to 0.0030 | mg/kg | Same | Abstract |
| Mean cadmium (Cd) range (ROW crops) | 0.0008 to 0.0027 | mg/kg | Same | Abstract |
| Mean Cu range (ROW crops) | 7.99 to 9.37 | mg/kg | Same | Abstract |
| Mean Zn range (ROW crops) | 16.17 to 77.51 | mg/kg | Same | Abstract |
| Max child EDI, Zn in cocoyam | 7.9 × 10^-1 | mg/kg per day | Children | Abstract |
| Max child EDI, Cu in cocoyam | 1.0 × 10^-1 | mg/kg per day | Children | Abstract |
| Max child EDI, As in cocoyam | 9.5 × 10^-5 | mg/kg per day | Children | Abstract |
| TLCR for arsenic | 1.5 × 10^-5 | dimensionless | Children consuming cocoyam | Abstract |
| USEPA acceptable CR limit | 1 × 10^-6 | dimensionless | Reference | Methods |
| LOD, lead (Pb) | 1.73 | µg/L | Analytical | Methods |
| LOD, cadmium (Cd), Cu, Zn | 0.02 | µg/L each | Analytical | Methods |
| LOD, arsenic (As) | 2.0 | µg/L | Analytical | Methods |
| Spike recovery range | 92 to 107% | percentage | QC | Methods |
| RSD | less than 5% | percentage | QC | Methods |
Methods (brief)
48 food crop samples from 12 each of yam, cassava, cocoyam, and waterleaf, all from Ibaa Community ROW zone plus matching control samples from an uncontaminated reference site. Edible portions acid-digested with HNO3/HClO4 (3:1). Analysis by graphite furnace AAS (GF-AAS; Hitachi Z-2000) for arsenic (As), lead (Pb), cadmium (Cd), Cu, Zn. Ingestion rates: adults 100 mg/day, children 200 mg/day. Exposure duration: adults 30 years, children 6 years. CRM: NIST SRM 1570a spinach leaves; recoveries within 8% of certified values.
Evidence fitness
This is an impacted-site study; the contamination levels reflect active petroleum pollution from pipeline ROW operations and are substantially higher than background agricultural soils. Results cannot be used as ambient or typical market-level contamination estimates for Nigerian staple crops. The arsenic TLCR exceeding 10^-6 for children consuming cocoyam from the ROW zone is a food safety concern specific to this contaminated community. The study is relevant to source-attribution and impacted-community pages but should not be used to set general dietary intake benchmarks.
Limitations
Impacted-site design limits generalizability. All 48 samples from one community. No longitudinal data to assess trend or remediation effectiveness. Speciated arsenic (inorganic vs. organic) not reported; total arsenic used for carcinogenic risk estimate may overstate risk.
Related evidence
Update history
No substantive edit history is available in this build. The full commit record is available in git.