Review of Environmental and Public Health Impact of Automobile Wastes and Automobile Transportation in Nigeria

Automobiles are machines designed for transportation; it is a self-propelled vehicle with power source for its propulsion and is used for transporting. Most vehicles imported into Nigeria are rickety and are mostly out of use, and since there is no regulation with regard to quality and quantity of vehicles to be imported coupled with lack of technology to deal with automobile waste, large volumes of automobile waste dot the Nigerian landscape. Negative environmental and public health issues of automobile waste and automobile transportation result from the fact that its several components (metals, metalloids, polymers, etc.) on decomposition or expiration release toxic substances such as phenols (C 6 H 5 OH), benzene (C 6 H 6 ), polycyclic aromatic hydrocarbons (PAHs), and so on into the environment, while on operation, automobiles are the most significant source of air pollution as unburnt diesel releases particulate matter (PM 2.5 , PM 10 ), oxides of carbon, oxides of nitrogen, oxides of sulfur, volatile organic compounds (VOCs), smoke, soot and ash particles, metal oxides, as well as nitrate and sulfate groups. The aim of this work is to explore and draw out salient points from previous literature with regard to detrimental environmental and public health issues of automobile wastes and automobile transportation.


Introduction
An automobile is a machine whose ultimate designed function is to transport men and goods. It is also called a motor car [1]. It is a self-propelled vehicle which contains the power source for its propulsion and is used for transporting passengers and goods on the ground, such as car, bus, trucks, articulated vehicles, etc. It is also a transportation equipment unit which consists of a frame supporting the body and certain power developing and transmitting units which are further supported by tires and wheels through springs and axles [2]. An automobile is simply

Components of an automobile
Since the seventeenth century, several attempts have been made to design and construct a practical operative automobile. To achieve the purpose of making a vehicle move, various constituents' materials combine to form an automobile. There are six major components of an automobile. They include the following:

The super structure or the body structure (frame)
This includes the chassis which supports the engine, wheels, body, braking system, steering, etc. It is the main mounting support for all components including the various parts of the body of a car. It deals with the static and dynamic loads without undue deflection or distortion [2]. Other parts of the body includes the bonnet (hood), bumper, cowl screen, deck lid, fender, header panel, radiator core support, Environmental Factors Affecting Human Health grille, roof rack, rims and hubcap, spoiler, fuel tank door, trunk, door, door seal, door handle, door latch and hinge, door water shield, tire; central locking, window motor, window seal, windscreen, sunroof glass, fuel tank, horn, trunk accessory, and wing mirror and glass.

The transmission system
The main function of transmission system is to transfer power from engine to rear wheel via gearbox to obtain the various gear ratios [13]. The speed and torque of the wheels change in relation to the speed and torque of the engine due to the gears in the transmission. They include clutch assembly (clutch lining, clutch disk, clutch fork, clutch plate, clutch cable, clutch fan, clutch hose, clutch shaft, clutch spring and clutch pedal) [14], gear assembly (i.e., gear pump, gear ring, gear shift lever knob, gear couplings and gear box, which contains the idler gear, knuckle, master cylinder, bearings, counter or output shaft, pinion, and gear set), propeller or drive shaft, rear axle shaft, trans-axle housing, differential set (i.e., spider gears, differential seal, pinions, differential flange and differential clutch), speedometer, transmission set (i.e., transmission gear, transmission seal and transmission spring), flywheel ring gear [1], shift valve, speed reducer or governor and wheel and torque converter [9].

The internal engine system
This part of the automobile is designed as an engine. It is a device which converts chemical energy from fuel through combustion with air (inside a combustion chamber) into mechanical energy with the use of other components in the engine. The internal engine supplies the power which is delivered by the transmission system to the wheels through the clutch or fluid coupling [2]. The system is subdivided into three parts: i. The engine components, which includes engine the block [15], engine shake damper, vibration absorber, fan belt, gudgeon pin, piston (i.e., piston pins, crank pin, piston pin brush, and piston ring), engine valve, harmonic balancer, accessory belt, petrol engine, camshaft assembly (i.e., camshaft bearing, camshaft fastener, camshaft locking plate, camshaft push rods, and camshaft phase variator), air duct, connecting rod (i.e., connecting rod bearings and bolt), crankshaft [9], crank case, crank pulley, crankshaft oil seal, distributor, drive belt, cylinder head (attached with cylinder head gasket and cylinder head cover parts), rocker arm, rocker arm cover, starter motor (starter pinions and rings), air blower, turbo charger and super charger, radiator parts (radiator, radiator gasket, radiator pressure cap, overflow tank, thermostat, radiator bolt), water tank parts (water tank, water pump, pump gasket, and water pipe), oil system (oil filter, oil pan, oil gasket, oil pipe, oil pump, and oil strainer) and valve springs and valve seal.
ii. The exhaust system, which includes exhaust pipe, muffler (or silencer), exhaust manifold and exhaust manifold gasket, heat shield, exhaust clamp and bracket, exhaust flange gasket, catalytic converter, resonator and spacer rings.
iii. The fuel system, which includes, air filter, carburetor, choke cable, fuel cap, fuel cell component, fuel distributor, fuel filter and fuel filter seal, fuel pump, fuel injector, fuel injector nozzle, fuel cooler, fuel pump and gasket, fuel pressure regulator, fuel rail, fuel intake manifold and gasket, fuel tank, throttle body and fuel water assembly [15].

The auxiliaries
This part of an automobile consists of all the electrical and electronic components and battery system. They include audio/video devices (i.e., antenna assembly and cable, radio media player, video player, tuner, speaker), voltage regulator, alternator, gauges [22] (such as ammeter, odometer, manometer, hydrometer, oil pressure gauge, speedometer, water temperature gauge, pressure gauge, fuel gauge, vacuum gauge, tire pressure gauge, etc.), thermostat, ignition box, ignition coil, sparking cable, distributor cap, electronic timing controller, calibrator, remote lock, engine compartment, starting system (starter solenoid, door switch, ignition switch, switch cover, glow plug, and starter motor) [23], lightning (spotlight, interior light and lamps, headlight, fog light, trafficators, turn-signal control, license plate lamp and bulbs), sensors (air bag sensor, coolant temperature sensor, throttle position sensor, crankshaft and camshaft position sensor, fuel pressure sensor and automatic transmission speed sensor), navigation/GPS navigation device system, central locking system, battery system (battery box, battery cable, battery control system, battery plate and battery cap), sulfuric acid and distilled water [22].

Car interiors
Dash panels, secret compartment or trap, car seat, seat belt, seat cover, arm rest, bucket rest, head rest, carpet and floor materials, children and baby seat, and bench rest [24].
Environmental Factors Affecting Human Health 6

Chemical constituents of some parts of an automobile
The automobile industry uses a tremendous number of materials to build cars, including iron, aluminum, plastics, steel, glass, rubber, petroleum products, copper, steel, etc. In all there are more than 6000 (>600) components of an automobile. These parts are used to create everything from the small parts such as dashboard needles and wiring to the big parts such as the engine block or the transmission gears. Due to the high demand of automobiles and technological advancement, suitable materials have been used for the production of automobile components that are durable and serve the purpose of the automobile. Some of the chemical components of the various automobile parts are tabulated below:

Menace of automobile workshops
Due to poverty and the dire need to own vehicles for ease of movement, these aging vehicles still attract customers from Nigeria's middle class and those at the lower rung of the economy [8]. Large numbers are taken to automobile workshop for repair and refurbishing. Automobile workshops are important considering public health issues because they are carried out in poor environmental settings coupled with lack of safety and hygienic lifestyle (eating with unwashed hand, wearing of dirty and contaminated workshop clothes for a long time, etc.) of workshop artisans, yet it is a beehive of activities because it has become the source of employment to several informal sector workers such as auto repair, servicing and refurbishing, auto parts scavenging, car wash, tire pumping and repair, autoelectrician, wheel balancing and alignment, oil sales and servicing, spare parts sales, water and food vendor, etc. [6][7][8]. Apart from esthetic pollution, automobile workshop contributes significantly to environmental and public health discourse. Several literatures have documented that pollutants such as heavy metals [41], benzene, nitrobenzene, gasoline fumes, exhaust gases, particulate matter, etc. are released by activities at auto workshops and automobile and have negatively affected surface and underground water and adjacent farmlands [42][43][44]. In major Nigerian cities, automobile workshops are in clusters along major roads comprising unregulated activities such as automechanics and panel beaters (car body work). Large expanse of would have been arable lands are occupied and polluted. Drainage system is blocked by waste generated from automobile workshops, heavy metals, waste oils, and noxious gases that are released into the environment, adjacent farmlands and food crops, which may possibly be contaminated by heavy metals and toxic substances. Exposed subjects at automobile workshops (auto technicians) are established to have high risk of cardiovascular and pulmonary diseases [45].

Automobile wastes
Importation into Nigeria of second hand ("Belgium") cars is second to none in Africa; therefore the Nigeria landscape is replete with many rickety and not road worthy, aging, and aged vehicles. Lack of spare parts and adequate technology makes repair and refurbishing of automobiles an uphill tax coupled with unfavorable weather condition such as high temperature (Nigeria been in the tropics), acidic rainfall and high relative humidity, acidic mist and aerosols [ unequaled and unprecedented high level road accident occasioned by poor road infrastructure and network, the net effect is that many vehicles are out of use and ultimately become waste. Recently wastes are regarded as "materials out of place" as against previous concept of "objects of non-usefulness." Automobile wastes are sometimes regarded as bulky waste, which include waste generated from servicing vehicles, automobiles, motorized trucks, and related equipment; they are made up of waste battery, scrap metal, used motor oils and lubricants, hydraulic fluids, bottom sludge, old motor parts, greases, waste engine oil, paints, petrol and diesel, which are generated and disposed indiscriminately. Abandoned vehicles dot Nigerian environment (workshops, roads, institutions, homes etc.) where they are left to the vagaries of weather to decompose and release some toxic substances, documented in Table 1, into the environment (Figures 1 and 2).

Greenhouse effect, global warming and acid rain
Greenhouse gases are gases that are capable of absorbing infrared radiation emitted from the earth's surface and reradiate them back to the earth surface.
The major component chemicals of greenhouse gases (GHGs) include hydrocarbons (HC), oxides of nitrogen (NO x -NO, NO 2 , N 2 O 3 , NO 3 ), oxides of carbon (CO x -CO, CO 2 ), particulate matter, sulfur dioxide (SO 2 ), photochemical oxidants and water vapor (H 2 O), ozone, and chlorofluorocarbon (CFCs) [48]. All these gases are in higher concentration released into the atmosphere by automobile emission and decomposing automobile waste irrespective of transportation mode [49]. Negative health effects associated with high concentrations of greenhouse gases already documented include asthma, respiratory distress, cancer, birth defects, low birth weight in children, genetic mutations and premature death [50,51]. The resultant effect of higher concentration of greenhouse gases in the tropospheric region of the atmosphere is the increase in the air temperature. Anthropogenic activities destroying the ozone layer contributing to global warming stem from manmade compounds and chemicals with high global warming potentials (ozone layer destroyer) [52,53]. Synergistic effect of global warming is much evidenced on melting of global ice stacks (glaciers), rise in sea level, and flooding of coastal regions. Three gaseous compounds (CO 2, SO 2 , and NO 2 ) emitted by automobiles are of the compounds known as acid anhydride of which SO 2 and NO 2 are outstanding for they significantly contribute to acid rain. Exposure to ambient concentrations of CO can have resultant formation of carboxyhemoglobin together with inhaled particles, which increase blood viscosity, thereby hampering oxygen delivery to the tissues [54]. A direct effect of gaseous emission by automobiles is acidic precipitation which affects terrestrial and aquatic ecosystems with attendant public health implication as has been widely reported in Nigeria [46,47,55]. Depending on the soil in nature, acid rain affects the soil. Acidic precipitation dissolves organic matrix and mineral matter largely present in the soil, which are K + , Ca 2+ , Mg 2+ , Na + , and anions (HCO 3 − , SO 4 2− , Cl − , CO 3 − ); these replaces the hydrogen of the acid rain and make the soil acidic. The pH of surface water may not change much due to acid rain because of the counterbalancing effect of water chemistry. Apart from acidic precipitation caused by SO 2 and NO 2 emitted from automobiles, minor concentration of SO 2 in air causes respiratory tract problem, irritation, secretion of mucus, and death at increased level of 500 ppm. NO 2 causes lung tissue inflammation at (50-100 ppm) exposure levels, bronchitis fibrosa obliterans (150-200 ppm) exposure, death (550 ppm) exposure [56]. Skin cancers and lesion, stomach ulcers, ocular congestion or corneal problems, and epithelial cell or leukocyte damage are possible health challenges associated with exposure to acid rain [55,57]. The above chronicled facts show that emission from automobile transportation can synergize change in climate (alteration between balance in incoming and outgoing radiation elements over a period of time in the atmosphere leading to differed quality of air over time) [58] and that climate change is intricately weaved to human health.

Public health issues associated with automobile waste and automobile transportation
For the fact that automobiles are the most important vital means of transportation owing to their ubiquitous nature, portability, flexibility, comfort, Environmental Factors Affecting Human Health and affordable cost (when compared with trains, ships, and airplanes), more and more people all over the world are purchasing vehicles for their personal, office, and company use. Some families have as much as two, three, four, etc. depending on their purchasing power. In Nigeria, the Federal Road Safety Corps (FRSC) stated that there are more than seven [8] million vehicles on Nigeria road [59]. The automobiles are helpful to human population, and they can transport people and goods to places of need such as offices, markets, schools, sporting events, hospitals, leisure centers, etc. This is made possible by adequate road network interconnecting the cities and the rural communities. The inevitable effect is the numerous public health issues associated with automobile transportation. The use of premium motor spirit, diesel, paints, and other gaseous materials [45] has led to the increased pollution and negative health effect. Incomplete combustion of fuel due to lack of air, poor mixing of air with combustion gases, and low combustion temperature lead to particulate matter emission; the whole property is a function of operating condition of the engine, lubricant oil, fuel composition, and the gas filtering equipment [60]. Substances that can be emitted from automobile exhaust include CO, H 2 , CO 2 , H 2 O, hydrocarbons (CH n ), volatile organic compound (VOCs), oxides of sulfur (SO x ), oxides of nitrogen (NO x ), particulate matter (PM 2.5 and PM 10 ), soot [61], and metals such as vanadium, lead, nickel, cadmium, potassium, sodium, phosphorus, lead, zinc, copper, manganese, iron, barium, etc. [60,62]. Other possible constituents of automobile exhaust emission include benzenes, polycyclic aromatic hydrocarbons, etc. The list above is considered as the exhaust emission, while the evaporative emissions are the vapors of fuel which are released into the atmosphere unburnt. The car exhaust emission has a great deal of negative effect on the human health and the environment. Car exhaust pollutants cause coughing, breathing difficulties, eye irritation, and distress to the respiratory system (throat, lungs, and chest). Specifically, heavy metals such as lead cause an occupational potent widespread human and environmental toxicant produced by burning leaded fuel and can interferes with normal functioning of red blood cells, thus hampering important enzymes in the body, damages and shortens the lifespan of red blood cell and cause anemia. Serious exposure burden can cause renal dysfunction, fatigue, arthritis, birth defects, hallucination, psychosis, autism, etc. [63]. Severe exposures to cadmium cause tracheobronchitis, pneumonitis, pulmonary edema, contacting cadmium by inhaling of cadmium-laden smoke fast rack respiratory, kidney, liver and bone damage. The bone becomes tender (osteomalacia), depletion of mineral density (osteoporosis) which accentuate backbone and joint pain, thereby increasing the risk of fractures [64]. Irritation of the nose and throat, headaches, dizziness, body weakness, cough, chest pain, and chills are inflammatory symptoms. Cadmium and its compounds are also carcinogenic. Nickel, when in the body, can alter its chemical nature but cannot be destroyed, and its binding to form ligands and transportation throughout the body depicts nickel metabolism. Interference of nickel with zinc, manganese, magnesium, and calcium physiologically is regarded as its toxicity [65,66]. Myocardial infarction, acute stroke, and burn injury are disease conditions linked with altered serum concentration and transport of nickel [67] inhaling automobile smoke laden with nickel can lead to high accumulation in the lungs, nasal septum, liver, and kidney [68]. Erythrocytes and leukocytes inhibited production, blood vessel damage, vomiting, irregular and abnormal heartbeat, which are caused by short-term exposure to reduced concentration of arsenic. Malfunctioning of cells, respiration, enzyme cell, and mitosis are caused by arsenic because it is a protoplasmic poison; the main effect is on the sulfhydryl group of cell [69]. Documented toxicological and health Review of Environmental and Public Health Impact of Automobile Wastes and Automobile… DOI: http://dx.doi.org /10.5772/intechopen.88491 effect of manganese include decrease in semen quality [70] and Parkinsonism [71,72]. For the fact that manganese is recognized to have different neuronal deficits such as learning disabilities, emotional liability, hallucination, compulsive behaviors, attention disorders, low fetal birth weight, and infant mortality [72][73][74], it is regarded as a potent toxin. The mucous membrane is the major target of inhaled hexavalent chromium or chromium-containing compounds, and then it synergizes asthmatic reaction, bronchial cancer, ulceration, and perforation of the nasal septum [75]. Although the human body for its physiological process requires copper in trace amount, increased exposure to copper through inhalation of automobile smokes/fumes will lead to copper toxicity such as early childhood liver cirrhosis (ECLC) and gastrointestinal symptoms [76]. The ubiquitous nature of polycyclic aromatic hydrocarbons emanates from natural processes such as forest fires, oxidation of biogenic precursors, unburnt petroleum products and other anthropogenic factors, which are released into the environment [77]. PAHs are hazardous chemicals that negatively impair human health [78,79]. Accordingly, automobile transportation is a veritable source of PAHs in the environment being an anthropogenic pollutant, and the urban atmosphere is laden with PAHs originating from incomplete combustion of fuel in the transportation engine [80]. PAHs being highly lipophilic and insoluble in water persist in the environment (air, water, and land), and many of its compound are known carcinogenic, mutagenic, and teratogenic to organism [81].
Particulate matter (PM 2.5 and PM 10 ) are tiny suspended microscopic particles like dust, soot, ash, solid/liquid objects, gases, and aerosols that can originate from daily life activity. They can travel long distance in air been less dense than air. Those that originate from automobile/diesel engine exhaust may consist of complex mixture of organic molecules (conjugated and straight chain), incompletely burnt carbon, oxides of metals, acid anhydrides, and phosphate, nitrate, and sulfate group. The respiratory system is the major attack site of inhaled particulate matter. Penetration of inhaled airborne particles through the airways increases with the increasing reduction in particle size for those >0.5 μm [82]. The health effect from inhaled particulate matter may be affected by the site of deposition within the respiratory system. Deposited particles within the respiratory system are influenced by biological, physical, and chemical process which includes dissolution into body fluids with absorption by blood, migration into cells by phagocytosis, and movement with mucus and blood fluid [83]. Cancer, asthmatic allergies, inflammation, cardiovascular and respiratory disease, and mutagenic and teratogenic effects are health issues associated with particulate matter inhalation [84]. Bronchovascular disease has been reported among subjects exposed to welding aerosol [85]. Cancers of larynx, nasal cavities, and paranasal sinuses were established in subjects exposed to and inhaled chromate paints [86,87]. Pollution keratoconjunctivitis (PKC) was reported among children in hydrocarbon processing in Niger Delta area of Nigeria [88]. Among automobiles, it is established that twowheeled vehicles (motorcycles) emit more particulate matter into the ambient air than four-wheeled vehicles (cars) and therefore more polluting effect. This fact can be exacerbated in cities with high traffic gridlock (traffic congestion) as vehicular emission poses great threat to environmental and public health. The united nation (UN) 1998 report states that over 600 million people are exposed to hazardous effect of traffic-associated pollutants after 21 years; this figure must have increased.

Conclusion
High voluminous importation of aging and rickety automobiles with engines of questionable combustion efficiency, weak and deplorable road Environmental Factors Affecting Human Health infrastructure, and high road accidents leading to automobile breakdown and favorable elements of weather (high temperature, acidic rain fall, dew, etc.), decomposition of automobiles, and release of toxic substances into the environment is inevitable, and this is coupled with toxic substances emitted by combustion of fuel/diesel during transportation. For the fact that Nigeria lacks adequate technology to deal with automobile waste, including recycling, there is a need to put in place, strengthen, and implement legislation regime so as to regulate the importation of automobiles into the country. Nigeria with a population of over 180 million people provides a large market for auto manufacturers. The government can negotiate with the manufacturers to establish a recycling plants, and this can remove large volume of auto-waste from the roads. The government can also assist the citizens to purchase new vehicles rather than fairly used ones through car loans. Adequate monitoring program by vehicle inspectorate officers to ensure road worthiness of vehicles. Tax incentives can be given to citizens who agree to limit car ownership to one. The government can also establish a comprehensive mass transportation network system that can convey large number of people on a daily basis. This can reduce the number of vehicles plying the road on a daily basis. Periodic air quality monitoring can be carried out to determine the levels of carbon (II) oxide, carbon (IV) oxide, oxides of nitrogen and sulfur, particulate matter, etc. in the air. Alternatively, non-fuel means of transportation such as beast of burden, bicycles, and trucks can be resuscitated and can lead to a significant reduction in number of vehicles on the road, meaning a decrease in pollution level and minimal health risk. The conclusion is that automobile waste and automobile transportation have some negative effect on the environment and public health.