This study assessed nutrients and microbial contamination in water and soil samples from Chileka Township, Blantyre
City, Malawi. Elevated total and fecal coliforms (1300 cfu/100 mL and 290 cfu/100 mL) in groundwater (GW), and
(34,000 cfu/100 mL and 8000 cfu/100 mL) in surface water (SW) were found, representing a risk of exposure to waterborne
disease. While the criteria in the Malawi Standard for raw groundwater was mostly met, water from only 20% of the
boreholes complied with the WHO requirements. Nitrate (
NO3
─) and Cl
─ (47.8 mg/L and 263 mg/L) exceeded the WHO
limits in GW. Cadmium (Cd) occurred in a few cases at concentrations up to 0.217 mg/L and 0.138 mg/L in GW and SW.
Lead (Pb) and Cr were below detection limits, while Mn (0.319 mg/L and 0.640 mg/L) in GW and SW, and Fe (6.92 mg/L)
in SW compromised taste. Though bacteriologically unfit for raw consumption by humans, both GW and SW chemically
met FAO-acceptable limits for irrigation, and standards for livestock watering. The NO3
─ and PO4
3─ maximum concentrations
in soil were 58.9 mg/kg and 506 mg/kg, respectively. Lead (Pb) and Cd were not detected whereas Cr, Zn, Cu, Mn
and Fe in soil were 27.7 mg/kg, 190 mg/kg, 60.4 mg/kg, 1307 mg/kg and 6552 mg/kg, respectively. Magnesium (Mg),
Ca, Na and K were 20,523 mg/kg, 22,334 mg/kg, 544 mg/kg and 5758 mg/kg, respectively in soil. The human health risk
assessment results, on the other hand, showed that at least 30% (6 out of 20) of the GW samples and 60% (3 out 8) of the
SW samples had HI > 1 for adults, children and infants, indicating existence of non-carcinogenic risk. Similarly, at least
15% (3 out 20) of the GW samples and 18% (1 out of 8) of the SW samples had CR > 0.001 for adults, children and infants,
suggesting a risk of developing cancer during a lifetime due to Cd exposure. Though both GW and SW are generally of
good chemical quality, chronic exposure to nitrate and cadmium is a health risk in the area. The current trace metal levels
are not worrisome, but soil nitrate and phosphate may need regular monitoring.