Chapter 10. Status of soil pollution in Near East and North Africa
Main health problems associated with pollution in Near East and North Africa
Several soil contaminants have been reported to threaten public health in the NENA region. Some examples of health problems associated to the major sources of soil pollution in the NENA region are presented below.
10.4.1. Health problems associated with contaminated air and dust
Road dust quality in Jeddah City, Saudi Arabia, showed a high concentration of trace elements, notably cadmium, arsenic, and lead (Shabbaj et al., 2017), posing a health risk for children and adults. Chromium, cobalt, copper, iron, manganese, nickel, vanadium, and zinc were detected in the following types of area (ordered from highest to lowest concentrations): dense traffic areas, parking-lots, residential, mixed residential and commercial, suburban, and rural. The analysis of trace elements from potentially polluted playgrounds and soils from 20 schools in urban and rural areas in Mashhad, the Islamic Republic of Iran, revealed soil pollution by lead in urban schools soils and by arsenic in rural schools. Based on the limits specified by the US Environmental Protection Agency, the authors related this accumulation of trace elements in schools to the impact of traffic in urban areas and agriculture in the countryside (Namavar and Hamidian, 2018). Children exposed through inhalation or digestion of polluted soils may be exposed to a potential health risk. According to Keshavarzi et al. (2015), the Hazard Quotient5 and Hazard Index6 obtained for street dust of Shiraz, Iran (Islamic Republic of) regarding mercury, lead, zinc, and manganese required special attention to prevent health risks.
Trace elements emitted by the transport sector ultimately settle on soils, affecting soil resources, plants and organisms. Some trace elements are toxic at a low level of exposure, and contaminants like nickel, cadmium and chromium have been linked to cancer in humans (Gupta, 2020). Mauritania, Kuwait and United Arab Emirates have been ranked among the countries with deadliest cities due to high levels of PM2.5 in the air, partly due to wind erosion of soils (HEI and IHME, 2019). In Mauritania, life expectancy is less than 60 years due to high dust content in the air. A recent assessment of the quality of roadside dust along the Abu Dhabi-Al-Ain road, United Arab Emirates, showed high levels of pollution by chromium (up to 1 540 mg/kg), cadmium (up to 0.7 mg/kg) and mercury (up to 0.9 mg/kg) caused by vehicles. The cadmium and mercury levels posed a potential health risk (Al-Taani, Nazzal and Howari, 2019).
Several studies addressed the risk of transferring trace elements from the soil to the food chain. In Egypt, Makarem, Amer and Naby (2019) analyzed 120 samples of raw cow’s milk and dairy products (Cream, Cooking butter, Kareish cheese, Damietta cheese, and yoghurt) from supermarkets and groceries. The high concentration of lead, cadmium and aluminium detected in milk and dairy products from the city of Alexandria, Egypt, confirmed the impact of soil pollution on the food chain. The concentration of trace elements was frequently found to exceed the permitted level under local guidelines and may pose a hazard to consumers’ health (cancer, immune system, haemoglobin deficiency), especially that of children (Shehab, Leboudy and Makarem, 2019).
A study assessed the genotoxicity to urban populations of organic extracts of PM10 emissions from oil refineries and heavy diesel vehicles in Jeddah, Saudi Arabia El Assouli, Al Qahtani and Milaat (2007). The PM analysis showed significant potential for DNA damage compared to similar samples from petrol-driven cars and residential areas. Occupational and residential exposure of residents to lead, zinc, copper, chromium, manganese, nickel and iron in the Industrial Estate of Aqaba, Jordan, revealed an average daily intake with a hazard quotient index5 above 1. This indicated a higher probability of adverse effects and exceeded the permissible limits for cancer risk for children and adults (Al-Shaweesh et al., 2019).
10.4.2. Health problems associated with inappropriate agricultural practices
Soil pollution affects soil biodiversity, nutrient balance and organic matter accumulation, which can cause a lowered soil ability to complex and fix trace elements that can then be transferred not only to groundwater but also to plants (Rodríguez Eugenio, McLaughlin and Pennock, 2018). Some trace elements such as molybdenum, zinc, copper, nickel and boron represent a phytotoxicity that can affect agricultural production and food security without direct risk to public health. Others such as arsenic, cadmium and selenium can accumulate harmlessly in plants with a direct risk to food safety.
Al Naggar et al. (2014) investigated the human health risks related to the accumulation of trace elements (copper, zinc, cadmium, lead and iron) in agricultural soils in four areas of Egypt (El-Mehala El-kobra, Kafr El-Sheikh, Kafr El-Zayat, and Al-Fayoum) and their subsequent transfer to clover blossoms and cotton flowers. The results showed a high concentration of cadmium and iron from industry and raw municipal effluents and sewage used for irrigation of crops (8 mg/kg and 1 000 mg/kg respectively) in arable soils. The accumulation of cadmium and lead in both crops exceeded the maximum permitted level of 3 mg/kg.
The application of nitrates or urea fertilizers to field crops, fruits and vegetables is essential in agricultural production. However, when applied excessively, nitrates tend to accumulate in fruits and vegetables, the continuous intake of which is associated with health risks of cancer caused by their metabolites. A recent survey was conducted in the Gaza Strip to determine nitrate residues in bread, fruits, vegetables and water samples taken from different locations. High nitrate levels were correlated with observed cancer cases (El-Nahhal, 2018). Results showed elevated nitrate levels in some bread samples and all fruits, vegetables and water samples. The local population had a high-risk of exposure to hazardous nitrates which potentially accounted for the growing incidence of cancer cases in the Gaza strip. It was recommended to control the leaching of nitrate form of nitrate-based fertilizers in agricultural areas, and encourage their replacement by other nitrogen-fertilizers from which nitrates are less prone to immediate leaching. It was also suggested that agricultural practices, including irrigation, should be controlled (El-Nahhal, 2018).
Soil and water pollution due to the misuse of fertilizers, and other agricultural and human activities in the recharge zones, can modify the hydrogeochemical characteristics of spring waters as detected in the Soreq-Catchment, West Bank, Palestine (Jebreen and Ghanem, 2015). This study showed high concentrations of trace elements (zinc, cadmium, manganese, arsenic, cobalt, copper, nickel, lead, aluminium, iron, and vanadium) that exceeded the permissible standards set by WHO in 2007. Due to the increased mobility of trace elements under redox conditions, the water from these springs was declared contaminated and undrinkable. In addition to persistent semi-volatile organic contaminants, the presence of nitrates and microorganisms in the shallow aquifer of Ramallah threatens the water supply of local communities, as groundwater is the main source of water for drinking and irrigation (Ghanem, 2005). In this way, contaminants that leach from agricultural soils end up in irrigation water and pollute other arable land in a closed cycle that harms both public health and ecosystem functions.
As mentioned in previous sections, banned pesticides are still widely applied in the region, as demonstrated by the large number of patients admitted to al Shifa and AlAhly Hospitals in Gaza with a diagnosis of severe poisoning caused by the use of banned pesticides (Alfarra and Hamada, 2019). Despite the observed increase in the number of cancer patients in the Gaza Strip between the 1970s and the 1990s (Figure 8), there are no available data on the concentration of pesticides in the soils and water bodies of the Gaza Strip. The only exception to this general lack of data is the analysis of several wells that was done in 1997 by Israeli laboratories. An overview study on pesticide misuse in the agricultural sector and its impact on food safety showed low levels of contamination in cucumbers and tomatoes in Palestine, Jordan and Egypt. In contrast, high levels were found in vegetables from Egypt and grapes from Jordan (El-Nahhal, 2004). El-Nahhal referred to several studies on accidental cases of pollution by organic contaminants and poisoning of local populations related to consumption of plant product in Morocco, Egypt, Iraq, Saudi Arabia, Sudan, Syrian Arab Republic, Jordan, United Arab Emirates and Yemen. Organic contaminants accumulate in food and pose a high risk for consumers as well as farm labours involved in its production.
Figure 8. Frequency of cancers registered in the Gaza Strip.
An extensive field survey and blood testing of farmers in Gaza, where about 130 different pesticides are used, identified that most showed symptoms of pesticide poisoning, with dizziness, headache, and nausea dominating, while the less dominant symptoms were vomiting, abdominal colic and running eyes (El-Nahhal, 2016). Some enzymes, such as acetylcholinesterase, are inhibited in farmers following long-term exposure to organophosphate and carbamate pesticides. Other enzymatic activities, such as alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase, were above the range that may damage liver and kidney cells after prolonged exposure, and result in hepatic-toxicity and nephrotoxicity. High levels of polychlorinated dibenzodioxins and polychlorinated dibenzofurans were detected in commercial 2, 4-D herbicide in the Palestinian West Bank territories (Dweik, Abu-Lafi and Odeh, 2005).
10.4.3. Health problems associated with industrial sources of soil pollution
Trace elements (lead, cadmium, arsenic and mercury) pollution of soil and water derived from industry and municipal wastes in the Northern parts of Egypt (Dakahlia, Kafr El-Sheikh and Damietta governorates) has been linked to the frequency of liver cancer. Elwakil et al. (2017) clinically examined 143 people who contracted hepatocellular carcinoma after consuming food produced on polluted soils. The concentrations of trace elements in the blood of these patients were much higher than in control subjects.
The recent rapid industrialization in Saudi Arabia has resulted in the direct exposure of a large number of workers to hazardous industries and has increased the number of populations indirectly affected by their emissions. Mustafa, Behiry and Mossad (2016) assessed the medical records of employees of 25 factories (glass manufactory, agricultural products, water pipe factories, polystyrene products, means plant for irrigation systems, manufactories of paper and paints products) in the industrial area of Qassim, Saudi Arabia. The results showed a significant increase in the rate of non-communicable diseases (cardiovascular diseases, eye, derma, and respiratory infection, hearing impairment, and diabetes) from 7.1 percent to 15.7 percent between 2011 and 2015. However, due to the high exposure of children to arsenic in traffic zones, a high risk for children comes from the ingestion of polluted soil particles or contaminated food products (Mustafa, Behiry and Mossad, 2016).
Gibson and Farah (2012) used an interactive survey of the local population in the United Arab Emirates to assess the impact of 14 contaminants on disease and premature mortality. The results were used to prioritize risk factors related to soil pollution and develop a strategic plan. The survey indicated that poor ambient air quality caused by the mobilization of polluted soil particles by wind erosion caused up to 650 premature deaths per year, while occupational exposure, poor food quality and pollution of the drinking water caused over 10 000 deaths per year. A national strategic mitigation plan was developed to address the risks of soil, water and environmental pollution, and 216 feasible measures were identified.
Adham, Al-Eisa and Farhood (2011) assessed the quality of soils in urban areas, such as Riyadh in Saudi Arabia, and the impact of the contaminants present on human health. They used rodents (Libyan jirds) as bioindicators to determine impacts to public health caused by trace elements (lead, cadmium and mercury). The results showed high levels of cadmium and mercury in the soil, which were 1.5 times higher than the environmental guidelines cited by Lee et al. (2009) (0.07 - 0.62 mg/kg for cadmium and 0.14 - 0.18 mg/kg for mercury). Each trace element behaved differently in the rodent’s body, accumulating in specific organs or specific sites, concentrating in the kidneys, liver and brain rather than in the lungs and heart. A tolerable level of copper and mercury was found in soft tissues of rodents, but a potential health risk can be associated with high levels of cadmium (up to 3.29 mg/kg), nickel (up to 1.48 mg/kg) and lead (up to 1.94 mg/kg) in soft tissues.
The results of a study on trace elements in the soils of the cities of Alexandria and Al-Musayyib, Babylon Governorate of Iraq, showed the concentration of nickel up to 200 mg/kg, with the highest single pollution index of 1.30. The pollution indices for arsenic and zinc were respectively, 1.68 and 1.45 (Al-Wotaify, 2019). Trace elements were linked to wastes from manufacturing military equipment, emissions from the thermal power station and urban wastes of various types. The residues and gases from the power station and factories are discharged into the air and subsequently settle on the soil surface. Accumulation in plants has shown a predominant zinc enrichment factor in the leaves and roots of alfalfa. Its use as fodder for livestock that later become food for humans is an example of an indirect pathway for the contaminants to transfer to humans.
Exogenous accumulation of lead radionuclides on the soil surface can potentially cause damage to health. The risks are from both soils near the source in industrial areas but also in places located along the prevailing wind direction, as the wind carries the dust particles onto which the contaminants have adsorbed (Saba et al., 2019). Phosphogypsum is a by-product of the manufacture of phosphate fertilizers and is enriched with radioactive uranium and radium (Alrawashdeh and Thyabat, 2012). During transport of the material radionuclides may be deposited along the road and may pose a direct and indirect ecological risk through emission and potential bio transfer (El Samad et al., 2014). An earlier study in Jordan pointed to the risk of radionuclides transfer to crops and showed a significant transfer of potassium-40 to apple trees (2.2 transfer factor) and a restricted transfer to wheat (0.9), while the transfer of uranium-238 showed a direct correlation with the amount of rainfall (Awadallah and Arafah, 2006).