From lifestyle to age, pesticides and herbicides: What really causes Cancer?

Phanice Okuso, 60, a retired nurse, conducting a breast cancer screening at Kakamega Oasis Multi-Specialty hospital. [File, Standard]

What really causes cancer?

This is the question that is before the High Court, with experts split over the cause.

On one hand, the government is opposed to 89 Kenyans seeking to join a class action case questioning the use of pesticides and herbicides in the country, claiming that what is sprayed is harmless.

Instead, the Pest Control Products Board insists that Kenyans are dying of cancer from being overweight and obese, while 94 per cent do not consume enough fruits and vegetables.

Dr Cyrus Githaiga, the board’s star witness, further claims that tobacco and alcohol use contribute to 13 and 19 per cent of cancer cases, while women get cervical cancer attributed to human papillomavirus (HPV), a sexually transmitted infection. He claimed that this data is derived from the Ministry of Health (MoH).

However, he alleges that glyphosate has low toxicity and does not present a hazard, adding that it is poorly absorbed through human skin.

According to him, the research done and submitted to court by the Africa Centre for Corrective and Preventive Action and lawyer Kelvin Kubai on the link between pesticides and herbicides and cancer was not cleared by the Institutional Scientific and Ethics Review Committee (ISERCs).

“Glyphosate does not accumulate or persist in the human body as alleged by the Intended petitioners/Applicants. Following ingestion, glyphosate is poorly absorbed, accounting for only 20 per cent of the administered dose. It is primarily eliminated from the body through faeces and, to a lesser extent, through urine within 48 hours,” claims Githaiga.

 The case follows a global debate on the use of synthetic chemicals in farms. Central to it is the use of weed and insect killers on farms. In the US, Bayer, manufactured by its subsidiary Monsanto, has been battling more than 65,000 cases in which plaintiffs who developed non-Hodgkin lymphoma accuse it of failing to label its weed killer Roundup as a cancer-causing agent.

The US blocked further cases, but the company is waiting for another ruling where it is seeking to pay out around Sh941.99 billion to thousands of persons who have sued in other Roundup cases.

Back home, Githaiga alleges that it is impossible to trace glyphosate in a person beyond "a few days".

He said that some of the persons who intend to join the case stopped exposure a long time ago, while others could not have had cancer from repairing carts used for transporting pineapples.

He holds the same opinion on paraquat. According to him, it is poorly absorbed and excreted within two to five days. He was of the view that it cannot occur only through deliberate suicidal ingestion and not occupational exposure.

“In vitro and in vivo studies on Paraquat do not support a mechanism of neurotoxicity associated with Parkinsonism, and similarly, the weight of evidence is insufficient to conclude the generic association between Paraquat and Parkinson's disease as alleged by the petitioner,” he says in his affidavit.

He argues that unless there is an independent review and forensic audit of the medical opinions and reports tendered by the intended petitioners, by qualified experts or a board appointed by the Medical Practitioners and Dentists Council, no one can ascertain the veracity of the clinical findings submitted in court.

Bayer and Monsanto, on the other hand, argue that the High Court has no powers to entertain the case. Instead, they assert that those who allege using the chemicals while at work ought to follow the WIBA pathway.

“The intended petitioners/applicants are seeking compensation for work injury claims and/or occupational safety and hazard claims,” they argue.

Sygenta East Africa Ltd says the intended petitioners ought to sue separately.

Agro Chemicals Association of Kenya is also opposed to the entry of persons alleging to have been affected. It argues that the case cannot be converted into a civil claim, where each person seeks compensation for a wrong.

 The Africa Centre for Corrective and Preventive Action and Kubai have Prof Zakayo Thumaita as their main witness. He faults Githaiga’s argument on glyphosate, saying that the claim that it cannot survive beyond 48 hours in a human body is a scientific misdirection.

“Modern toxicological research confirms that while free glyphosate in blood plasma may clear rapidly, chronic exposure results in deep tissue accumulation, bone matrix deposition, and disruption of cellular tight junctions. This leads to persistent systemic toxic effects and chronic low-grade cellular exposure that manifests clinically decades after the primary occupational contact ceased,” argues Thumaita.

A patient undergoes a breast cancer screening process. [File, Standard]

He submits that Githaiga’s argument about general age- related or lifestyle ailments fail to factor in peer reviews on the toxicity of glyphosate and its link to high blood pressure and glyphosate and neurotoxicity and Parkinson’s disease.

“Independent neurological studies conclusively establish the strong neurotoxic properties of glyphosate. Glyphosate crosses the blood-brain barrier, induces profound neuroinflammation, accelerates synaptic excitotoxicity, and triggers alpha- synuclein aggregation. This constitutes a direct, scientifically verified etiological pathway to neurodegenerative conditions, specifically Parkinson’s disease,” replies Thumaita.

 On Paraquat, the expert witness argues that safety realities are that those who use it are informed to use personal protective equipment. He further argued that the Pest Control Board has, over decades, failed to enforce strict use of the chemical.

“This assertion flies in the face of established agricultural safety realities in developing nations and local environmental contexts. The primary mechanism of Paraquat toxicity is driven by the generation of intracellular Reactive Oxygen Species (ROS) through continuous redox cycling. This induces catastrophic cellular lipid peroxidation, depletes mitochondrial NADPH pools, and causes selective, irreversible destruction of dopaminergic neurons in the substantia nigra. This is the precise, universally recognised pathological hallmark of Parkinson's disease.”

A National Control Strategy 2023-2027 indicates that cancer is now the third leading cause of death in Kenya, registering an annual incidence of 42,116 new cases and 27,092 recorded deaths.

Thumaita was of the view that 40 per cent of all cancers can be prevented by living in a healthier physical environment. “It demands a vigorous multi-sectoral approach to reduce environmental and occupational exposures,” he says, adding that although the Ministry of Health identifies promotion of intensive research into the role of pesticides, chemicals, and environmental toxins in cancer causation, the board wants to block judicial scrutiny of the same.

“Article 70 (3) of the Constitution of Kenya 2010 states that if a person alleges that a right to a clean and healthy environment has been denied or threatened, they may apply to a court for redress and the court may then make orders or give directions to provide compensation for any victim of a violation of this right, without the applicant having to demonstrate that any person has incurred loss or suffered.”

He insists that there is no labour or work injury issue with the use of pesticides and herbicides.