Abeokuta, Nigeria – In a ground breaking environmental investigation led by Professor O.O. Olujimi, one of Nigeria’s foremost environmental toxicologists, researchers have exposed the widespread contamination of groundwater by hazardous chemicals leaching from dumpsites across southwestern Nigeria.
The former Staff of the Department of Environmental Management and Toxicology, Federal University of Agriculture, Abeokuta and who currently work as Cultural, Natural and Environmental Programme Manager at the United States of America Air Force, United Kingdom a scholar of over 20 years teaching and researching experience reported from his recent study.
The study’s primary focus—Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs)—reveals a disturbing narrative of environmental degradation with serious implications for public health and ecological integrity. Covering six major dumpsites across Lagos, Ogun, and Oyo States, the research uncovers how open dumping practices and poor waste management are allowing these toxic compounds to infiltrate critical water sources, threatening the health of millions of Nigerians.
According to Professor. Olujimi who has been researching on impact of inadequate solid waste management in Lagos, Ogun and Oyo State since 2014 through research grants received from the Lagos State Government during Governor Babatunde Fasola regime and recently from the Tertiary Education Trust Fund, poor waste management result in soil, air, surface and groundwater pollution. PBDEs and phthalate esters have been reported in groundwater around selected dumpsites in Lagos and Ogun States.
A Region Under Threat: The Dumpsites in Focus
The team conducted sampling and analysis around the following six major dumpsites:
Lagos State: Olusosun Dumpsite, Ojota, Solous Dumpsite, Igando (including Solous 1, 2 & 3)
Ogun State: Saje Dumpsite, Abeokuta, Kurata Dumpsite, Sango-Otta
Oyo State: Ajakanga Dumpsite, Oluyole LGA, Awotan Dumpsite, Apete area
These locations represent some of the most densely populated and industrially active areas in Nigeria, which further complicates the waste pollution problem. Many of these dumpsites operate without engineered liners or leachate treatment systems—allowing contaminants to seep directly into the soil and aquifers.
PAHs: A Silent Infiltrator in the Water Table
Polycyclic Aromatic Hydrocarbons (PAHs) are compounds formed from the incomplete burning of coal, oil, gas, wood, or organic waste. The study found that these hazardous chemicals were present in both dumpsite leachates and nearby groundwater in significant concentrations—many of them exceeding World Health Organization (WHO) safety limits.
For example:
At Saje, the concentration of acenaphthylene in groundwater reached 54.96 µg/L, far above acceptable thresholds.
Benzo[a]pyrene, a potent carcinogen, was detected in concentrations that pose elevated cancer risks for adults and children.
These compounds are known to cause immune suppression, respiratory issues, developmental delays in children, and various cancers.
PCBs: A Second Wave of Danger
In addition to PAHs, Professor Olujimi’s team also analyzed the presence of Polychlorinated Biphenyls (PCBs)—synthetic organic chemicals once widely used in electrical equipment, paints, and building materials. Despite being banned in many countries, PCBs persist in the environment and are among the top 12 Persistent Organic Pollutants (POPs) identified by the Stockholm Convention.
The study’s results showed alarming PCB levels in both groundwater and leachates across the six sites:
Solous Dumpsite recorded the highest concentration of PCB3 in groundwater—338.99 µg/L, far exceeding acceptable risk levels.
Ajakanga Dumpsite showed significantly higher levels of PCB4 and PCB6, indicating heavy contamination likely from industrial and electrical waste.
Seasonal variations also impacted PCB concentrations, with dry season samples showing spikes in PCB3 and PCB4, possibly due to concentrated leachate during reduced rainfall.
These PCBs are linked to reproductive disorders, endocrine disruption, neurological damage, and several forms of cancer. Their bioaccumulative nature makes them particularly dangerous over long-term exposure.
What’s Leaking and Who’s at Risk?
The spatial distribution of both PAHs and PCBs demonstrated a clear pattern: groundwater sources closer to the dumpsites showed exponentially higher contamination levels. In several communities surrounding Olusosun, Solous, Saje, and Ajakanga, residents rely on boreholes for drinking and cooking water—placing them directly in harm’s way.
The health risk assessments, conducted using U.S. Environmental Protection Agency (USEPA) models, confirmed:
Carcinogenic risks (especially for children) were above the acceptable threshold (1×10⁻⁶ to 1×10⁻⁴) in multiple sites.
Non-carcinogenic risks, calculated via Hazard Quotient (HQ) and Hazard Index (HI), exceeded the safety margin (HI > 1) in most locations, particularly in Ajakanga and Awotan.
This toxic exposure, over time, could lead to kidney and liver damage, immune system suppression, skin lesions, and increased cancer incidence.
Unmasking the Source: Pyrogenic vs. Petrogenic Origins – Using advanced analytical techniques such as Principal Component Analysis (PCA) and diagnostic ratio modeling, the study traced the origins of these contaminants to two major pathways:
Pyrogenic sources, such as incomplete combustion of organic waste and fossil fuels. – Petrogenic sources, including petroleum leaks from waste trucks and dumping of industrial oils.
In Kurata, for instance, the diagnostic ratio suggested a predominance of petrogenic sources, while Awotan showed indicators of biomass and coal burning—reflecting the mixed-use nature of the waste deposited.
A National Crisis in the Making
What makes this research especially critical is its extrapolative value. While it covers six sites, Nigeria has hundreds of similar unregulated dumpsites. If the findings here are representative, millions across the country may be consuming or irrigating with contaminated water without even realizing it. The lack of institutional response compounds the threat. Although regulatory frameworks exist, enforcement remains weak due to funding shortages, limited manpower, and bureaucratic inertia. There is no national system for routine monitoring of groundwater near dumpsites.
Solving Nigeria’s groundwater pollution crisis goes beyond technology—it requires strong political will and public engagement. Prof. Olujimi recommends a five-step action plan.
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Government Action
Build proper waste systems, including lined landfills and leachate treatment plants to prevent toxins from seeping into the ground. -
Regular Monitoring
Set up a national program to check groundwater quality near dumpsites and industrial zones. -
Public Awareness
Educate communities about the dangers of drinking untreated borehole water near waste sites. -
Health Screenings
Provide medical testing and support for people already exposed to toxic chemicals. -
Polluter Accountability
Enforce strict laws and penalties for industries that dump hazardous waste into the environment.
Finally the recent findings reveal a dangerous truth lurking beneath our feet—groundwater contaminated with harmful chemicals like PAHs and PCBs. This isn’t just an environmental issue; it’s a national emergency.
As Nigeria continues to grow and industrialize, how the country handles its waste will shape its future. Clean water, public health, and environmental safety are all on the line. Therefore, groundwater is more than a natural resource—it is our lifeline. Protecting it means protecting our people, our economy, and the legacy we leave behind,” stated Prof. Olujimi.
