Assessment of Carcinogenic and Non-carcinogenic Health Risks of Metals in the Drinking Water of Gombe Local Government Area, Nigeria

Overview

Sule, Olowolafe, and Dabi assessed lead (Pb), Fe, Cu, chromium (Cr), Mn, and cadmium (Cd) in 87 drinking-water samples from Gombe Local Government Area, Nigeria, including tap, borehole, well, vendor, rainwater, sachet-water, and bottled-water sources. The paper reports source-type chronic daily intake, hazard quotient, hazard index, and incremental lifetime cancer risk outputs for adults, children, and infants. It is useful for drinking-water source context in Nigeria and for source-specific risk documentation, but the PDF does not print the underlying AAS concentration table, so the modeled risk outputs should not be used as benchmark concentration values.

Key numbers

Sample frame and source coverage:

Table 3 reports chronic daily intake (CDI) values by age group and water source. The highest source-type mean CDI values were:

Table 4 reports hazard index (HI) values. The source classifies tap, well, and sachet water as high non-cancer risk for all three age groups:

Table 5 and the surrounding text report incremental lifetime cancer risk (ILCR) for Cr, Pb, and Cd. Source-reported harmful-risk examples include:

Methods (brief)

The authors collected drinking-water samples across 11 wards of Gombe LGA using purposive sampling. They report analysis of Pb, Fe, Cu, Cr, Mn, and Cd with air-acetylene flame AAS using element-specific hollow cathode lamps. Health-risk outputs were calculated using chronic daily intake, hazard quotient, hazard index, and incremental lifetime cancer risk equations with USEPA-style exposure parameters for adults, children, and infants.

The paper states that metal concentrations were measured, but the PDF tables visible in the article provide exposure-model parameters and modeled risk outputs rather than a direct concentration table by water source. Treat Cr as total chromium unless a later full data table proves otherwise; the article does not report Cr(VI) speciation. It also does not report arsenic or mercury.

A methodological caveat applies to the Cr ILCR values: Table 2 lists a cancer slope factor of 41.0 mg L⁻¹/day for Cr, which is the USEPA IRIS oral slope factor for Cr(VI). The authors apply this slope factor to total Cr without speciation, which inflates the modeled ILCR for chromium relative to the value that would result from applying the Cr(VI) factor only to the hexavalent fraction. The paper’s headline conclusion that “chromium is the main cause of lifetime cancer” rests on that assumption.

Implications

Certification: Not a candidate benchmark concentration source because raw metal concentrations are not printed in the PDF; use as Nigeria drinking-water context and as a retrieval target for the missing concentration table.

Courses: Useful for explaining how source-type water sampling, metal concentration inputs, and exposure assumptions produce CDI, HQ, HI, and ILCR outputs.

App: Can support a context note that Gombe LGA tap, well, and sachet water were the highest-risk source types in this paper, while bottled water had the lowest modeled HI among the listed source classes.

Related evidence

• Water
• Bottled drinking water (purified, spring, artesian)
• Lead
• Cadmium
• Chromium
• Manganese
• Iron
• Copper

Update history

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