The use of mercury and lead by unregulated artisanal gold miners as well as abuse of pesticides and inorganic fertilisers in Kenya will be in focus as the country marks the World Soil Day on Wednesday.
Although attention has been on the easily detectible air and water pollution, concern is growing on the worsening quality of soil in parts of the country due to chemical contamination that even finds its way into food and other agricultural produce.
“Soil pollution often cannot be directly assessed or visually perceived, making it a hidden danger. The diversity of contaminants is constantly evolving due to agrochemical and industrial developments” the UN’s Food and Agriculture Organisation (FAO) said in a new report.
Data by the National Environment Management Authority (Nema) showed that soil pollution has become the second highest reported environmental crime in Kenya. In 2017, for example, the state agency recorded 23 cases of soil pollution, compared to 97 and 11 for air and water contamination, respectively.
With a fast growing economy, Kenya faces rising challenges of controlling land pollution. Poor urban planning and management of resources and poor enforcement of environmental laws have been blamed for the increasing cases of soil pollution.
Alarm over soil pollution is rising in Western Kenya regions such as Nyatike, Kakamega, Migori and Asembo where artisanal miners continue to illegally use metals such as mercury and lead in gold prospecting. Miners have for centuries used mercury to separate gold from rock or soil.
But when the heavy metal seeps into the soil, rivers and the food chain it causes serious health problems such as kidney failure, nervous breakdown and acute anaemia, which may not show symptoms for years, according to the United Nations Environment Programme (UNEP).
A newly published study by Sammy Koskei, Yuanyuan Cheng, Wei-lin Shi of China’s Suzhou University of Science and Technology said soil samples around Lake Victoria tested for high levels of lead metal of up to of 619 milligrammes per kilogramme.
The health effects of lead exposure range from intellectual disability, deafness, to kidney failure, the UNEP said. Lead is especially dangerous to children's developing brains — shortening their attention spans, triggering behaviour problems and impairing their ability to learn for the rest of their lives. High levels of lead concentration has also been recorded in Changwame, Mombasa, due to suspected illegal discharge of industrial waste.
In July this year, a court hearing a case in which some residents of Owino Ouru slum in Changamwe have sued for lead posoining, heard that the levels of lead concentration in the informal settlement is 53 times the accepted maximum of 1,200mg/kg.
“We were shocked by the revelation that up to 64,000 mg/kg of the metal was present in soil and dust samples. These levels are extremely high,” former Deputy Government Chemist Wandera Bideru told Environment and Lands Court Judge Ann Omollo.
The residents of Owino Ouru have sued the Attorney-General, the county government, cabinet secretaries for Environment and Health, as well as the National Environment Management Authority, Export Processing Zones Authority, Metal Refinery (EPZ) Ltd and Penguin Paper and Book Company.
The FAO said lead-based paint is a major legacy source of contamination in urban areas. “Soils become contaminated when lead-based paint is pulverised into dust or small particles during renovations or demolition and then enters the environment” it said.
The use of synthetic phosphorous and nitrate fertiliser to improve soil yields has also been flagged as a big source of soil pollution. The UN Food agency says nitrogen and phosphorus become pollutants when they are applied in excess to agricultural soils in the form of fertilisers, or in areas of intensive livestock production.
“These nutrients are able to leach into the groundwater or be transported to surface water bodies by runoff, causing eutrophication or leading to high nitrate concentrations and related environmental and human health problems” it said.
Analysts also warned that pesticides are harmful to the soil. Some are associated with heavy metal contamination of soils.
“The recent report by the Intergovernmental Technical Panel on Soils (ITPS) on the impact of plant protection products on soil functions and ecosystem services highlighted the severe impact of copper-based fungicides on earthworms and microbial biomass. These fungicides are widely used in organic viticulture to control vine fungal diseases” it said.