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Used tyres pyrolysis is an efficient solid waste management strategy for used tyres and a growing method of fuel oil production. However, the impact of air emissions associated at different temperature on ambient air quality has not been determined. To solve this problem, a pyrolysis fixed bed reactor and a condensing unit for separating liquid from produced gas were designed and constructed. 0.20 kg of used tyres were pyrolysed in the reactor and air emissions from the reactor chamber was characterized for air pollutants using the E-instrument E8500. Using a combination of measured mass of pollutants, mass of tyre pyrolzed and time taken during pyrolysis, Emission Factors of the air pollutants were established from the study at 200 °C, 300 °C and 400 °C. The concentration measured between 200 °C - 400 °C were in the range of 15 -7497 mg/m3, 0 – 4680 mg/m3, 38.25 – 103, 277.76 mg/m3 and 2 – 293 mg/m3 for CO, NOx, HC and H2S respectively. The developed emission factors were in the range of 16.52 – 8370.04 g kg-1, 0 – 4470.26 g kg-1, 42.126 – 104,055.9 g kg-1 and 2.20 – 322.69 g kg-1. The designed and constructed pyrolysis reactor and condenser unit were effective for used tyre pyrolysis while the measured air pollutants concentration were higher for all pollutants except H2S using the Federal Ministry of Environment (FEPA, 1991) standard. Hence, it is necessary to carry out further studies on air pollution control from waste tyre pyrolysis at lower temperature.

In many developing nations, wood is still commonly used as a fuel for domestic cooking. However, fuelwood combustion can have a pronounced effect on air quality by releasing considerable level of PAHs, thereby posing serious risk to global and environmental health. In this study, seven fuelwood samples were cut into small pieces (100 g) and subjected to open burning with a view to estimate PAHs emissions and their toxicity potentials. During combustion, sixteen basic PAHs were characterized by collecting gaseous emissions from the combustion on PUFs (Polyurethane foams) using probe from the air sampler. The PUFs were washed in a Soxhlet extractor with Acetone to extract the emission which was then analyzed using Gas Chromatography/Mass Spectrometry for characterization. Chrysene and Dibenzo[a, h]anthracene have the highest and lowest PAHs concentrations, respectively. All PAHs levels observed exceeded permissible limits of 1x10−6 and 1.2x 10−7 mg/m3 of European Union and World Health Organization, respectively. PAHs from cashew wood showed highest levels of toxicity and mutagenicity, while all the samples have the same carcinogenic effect, indicating that all the samples have the same environmental/harmful impacts, going by ∑PAHcarc/∑PAH ratios (ratio that indicates general harmfulness). The study concluded that despite the relatively low toxic, mutagenic and carcinogenic effects observed in this study, exposure to these concentrations for a long period should be avoided, especially for persons with existing known health conditions such as asthma, lung cancer and cardiovascular diseases.

High emission factor of identified air pollutants from the artisanal petroleum refineries in the Niger Delta region may be key to the degrading air quality of the region. This study determined air emission factor for the identified pollutants from the local refining technology in the region. The operational sites of these refineries are inaccessible due to security and proximity to raw material, making air quality evaluation and management impossible. However, Emission Factors are one of the best ways to quantify an activity-related air pollution especially in difficult terrain like those of the artisanal refineries. In this regard, air emissions resulting from the operation of these refineries were characterized/quantified with the use of E8500 Portable Industrial Combustion Analyzer. The measured concentrations were used to calculate the emission factors and emission rates for the identified air pollutants. The overall combined emission factors (g/kg) estimated in percentage of emissions for the pollutants characterized at the various unit operation, showed that; at the Oven Heating/Crude Oil Boiling Unit, HC had 52%, 41% for CO, 3% for NOx (NO + NO2), 2% for SO2 and 2% for H2S. Other process units emitted 53% and 55% for HC, 40% and 38% for CO, all 3% for NOx, all 2% for SO2 and all 2% for H2S for the Vapour Condensation and Refined Products Collection Units respectively. It therefore concluded that the high emission factors observed from the activities of these local petroleum refineries could be a contributing factor to the degraded air quality of the region.

The use of facemasks as a preventive measure against infection of the COVID-19 virus has some associated environmental impacts, especially in Subs-Saharan African countries where the used facemasks are being disposed of using open burning. Hence this study characterized Polycyclic Aromatic Hydrocarbons (PAHs) emissions from different COVID-19 facemask materials and determined the associated risk of open burning of facemask. Facemasks of different materials were sourced from open dump sites. Each material was combusted in an open reactor and the emissions were collected using A filter-sorbent sampling system. Analysis of PAHs in the sample was carried out using GCMS. The associated health risk was assessed using Incremental Life Cancer Risk (ILCR) and Hazard Quotient (HQ). The result showed the concentration of PAHs emission ranged ∑ PAHs 73.33 –368.16 µg/m3 while carcinogenic PAHs ranged ∑ CarPAHs 26.79–179.74 µg/m3. The result also showed the surgical and N95 facemask emits the highest concentration of PAHs. The modeled annual ground-level PAHs Isopleth reveals the presence of a high concentration of PAHs around the vicinity of the burning site after a year. Proper disposal of these facemask using controlled medical incinerator is highly recommended.

Background This study determined the levels of polycyclic aromatic hydrocarbons (PAHs) in the soil around typical automobile repair workshops in Nigeria. Risk assessment associated with human contact with the soil was carried out using hazard quotient (HQ) and incremental life cancer risk (ILCR) from human unconscious ingestion and dermal contact with the soil. Methods Soil samples were obtained at different automobile workshops in Ado-Ekiti, Western Nigeria. The PAHS in the samples were extracted using dichloromethane and extracts were cleaned up using silica-alumina gel open column chromatography. Analysis of PAHs in the soil was done using a gas chromatograph coupled to a mass selective detector operated on electron ionization mode. Results The results showed the mean PAHs concentration at the sampling locations ranged from 5.58 – 6.4 μg/g and the mean ∑ carcinogenic PAHs was 58.4 μg/g, equivalent to 59.39 % of total PAHs observed. The mean Toxicity equivalence (TEQs) ranged from 0.02 - 6.680 μg/g. Benzo (a) pyrene and dibenzo(a,h)anthracene have the highest toxicity equivalent. The total ILCRs from accidental ingestion and dermal contact in adults were 1 ×10^(-3) and 9.8 ×10^(-5), for adults and children respectively; both are higher than the permissible limit stipulated by the World Health Organization.The HQs obtained are several folds higher than 1. This implies high carcinogenic and non-carcinogenic risks for children and adults. Conclusions The study revealed the levels of PAHs and also revealed the risks associated with human contact with the soil around automobile repair workshops.

Adsorbents from chicken eggshells were synthesized by a simple method and used as a novel and effective adsorbent for the removal of carbon monoxide (CO) from an ambient environment. The synthesized adsorbents were characterized by X-ray fluorescence (XRF), Atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR), Proximate, ultimate analysis and adsorption isotherms. The characterization results showed that the presence of Ca, CaO, SiO2, CO, O-H, and O-Si-O stretching vibration bonding contributed to the adsorption capacity of the synthesized adsorbents. Chicken eggshells were collected, washed, and dried before being pulverized and sieved to yield 36 µm mesh particles. The eggshells were then separated into parts and treated to various calcination temperatures (700 °C, 800 °C, and 900 °C) with and without phosphoric acid impregnation. Therefore, seven different adsorbents were synthesized. An environmental chamber with a portable generator as the CO source was used to evaluate the performance of the adsorbent. For different residence times (2 to 10 min), different amounts of the synthesized adsorbents (varying from 5 g to 25 g) were introduced into the chamber. A combustion analyzer was used to measure the initial and final CO concentrations. All the synthesized adsorbents are effective in removing CO, but ordinary chicken eggshell has the highest (59.32%) CO capacity removal, the adsorption kinetics followed a Lagergren pseudo-first-order model, and the adsorption isotherms conformed to Langmuir equation.

Common charcoals from different wood species were collected, identified and prepared for analysis. Proximate analyses were carried out. The study aimed to characterize the identified charcoal and suggest the best charcoal that will give the minimal pollution effect. The result showed that the moisture content of the charcoal ranges between 3.26 and 8.40 wt% with an arithmetic mean of 5.36 ±1.50 wt%, the volatile content ranges between 3.05 and 13.62 wt% with an arithmetic mean of 7.20 ±3.55 wt%, the fixed carbon ranges between 76.83 and 90.57 wt% with an arithmetic mean of 83.54 ±4.60 wt%, and the ash content ranges between 3.09 and 5.18 wt% with an arithmetic mean of 3.87 ±0.70 wt%. The heating value of charcoal of different wood species were determined using Bomb calorimeter. Afzelia bipindensis has the highest ash content while Hevea brasiliensis has the lowest ash content. The heating value ranges 31.82–39.42 kJ/kg with a mean of 35.375 ±2.673 kJ/kg. This shows that Burkea africana could be best for use as a cooking fuel for households and restaurants because it has the best fuel property in terms of moisture content.

Laboratory simulations of the spill behaviors of three different Nigerian crude oil samples over three media (fresh water, sea water and soil) were carried out with a view to determining the effect of crude oil spillage on emission of fine (PM2.5) and inhalable particulates fractions (PM10). The spillage experiments were carried out in an environmental test box fitted with equipment to regulate the micro climatic conditions (temperature and Relative humidity). The maximum concentrations of PM2.5 were 711, 689 and 680 µgm−3 while those of PM10 were 972, 946 and 940 µgm−3 for sample A, B and C respectively. These peak concentrations were obtained for spill conditions corresponding to fresh water at 45 °C and 49% relative humidity. The least concentrations of PM2.5 and PM10 emitted across all samples were 63 µgm−3 and 256 µgm−3 respectively and these corresponded to spillage over sea water at 15 °C and 80% relative humidity. These concentrations clearly exceeded the short time averaging period (24 h) standards set for PM2.5 and PM10 by the United States Environmental Protection Agency. Incessant crude oil spillages in the Nigerian oil fields are therefore predicted to cause degradation of air quality within a short duration from the spill.

Total suspended particulates emitted during crude oil spill were investigated using laboratory simulation experiments. This was with a view to establishing the toxicity potentials of emitted particulates. Climatic and spill media conditions similar to those obtainable in real life were created in an environmental chamber and the total particulates emitted during spills involving three crude oil samples of Nigerian origin were measured with Quick Take sampler. The toxicity potentials of the emitted particulates were subsequently determined by dividing the 24- hour averaging period concentrations of the particulates by the statutory limit. The statutory limits used were those of Nigeria’s Federal Ministry of Environment (FMENV), World Bank and the World Health Organization (WHO). For temperatures between 15 ºC and 35 ºC and spill media (over fresh water, sea water and soil), the extrapolated 24 – hour averaging period concentrations ranged between 186.79 – 584.28 μgm-3, 186.98 - 584.48 μgm-3 and 247.40- 350.21 μgm-3 for sample A; 183.44 – 571.99 μgm-3, 183.63 -572.19 μgm-3 and 244.05-337.92 μgm-3 for sample B and 178.41 – 566.96 μgm-3, 178.61 - 567.16 μgm-3 and 332.89- 280.60 μgm-3 for sample C. The observed TSP concentrations breached the WHO (lower limit) and World Bank limits at all temperatures and over all spill media and consequently the toxicity potentials exceeded 1.0 which were indications of hazards to human health. The study concluded that particulate emissions during crude oil could be high enough to pose threats and suggested adequate protection for cleaning up workers.

This study investigated the contribution of anthropogenic emission of benzene from petroleum refineries to the Nigerian’s ambient air quality with the view of understanding the impact of petroleum production facilities on host airshed. The Activities of the four existing and 22 proposed petroleum refineries in Nigeria were obtained from the Department of Petroleum Resources and these were combined with emission factors of different units at the refineries to estimate benzene emissions. No-control-measure option (worst case scenario) was assumed because of lack of information on control efficiency of the refineries. The study revealed that two of the existing refineries in one of the oil-producing cities in Nigeria released a total of 10.01 × 1011 tons/year of benzene into the ambient air of the city, apart from additional 2.35 × 1013 tons/year anticipated to be released from three of the proposed refineries into the ambient air of the same host community. If operated at full capacity, the estimated benzene emission from the four existing refineries stood at 5.50 × 1013 tons/year while the 22 proposed refineries have the capacity of releasing additional 16.73 × 1013 ton/year. On the overall, the contribution of benzene from refineries on yearly basis to Nigerian airshed was estimated to be 22.24 × 1013 tons. These concentrations if not checked could lead to devastating environmental issues. Some mitigating measures were suggested to control and subsequently abate benzene emission from these refineries.

Environmental hazards associated with release of emission from petroleum refineries have caused serious concerns for the host communities. The study focused on the assessment of the contribution of Nigerian refineries to the ambient air quality. Total emission of toluene, ethyl benzene and xylene (TEX) from Nigerian twenty-six (four existing and twenty-two proposed) refineries were estimated using emission factor approach, under no-control measure (worst case scenario) option. Results showed that the four existing refineries emit 2.90 × 1013 tons of toluene, 1.93 × 1013 tons ethyl benzene and 1.06 × 1013 tons per year while the twenty-two proposed refineries have the capacity of releasing annually 9.17 × 1013 tons of toluene, 6.69 × 1013 tons of ethyl benzene and .95 x 1013 tons of xylene. If operated at full capacity, the total estimated TEX emission from the existing refineries stood at 5.89 × 1013 tons/year while the proposed refineries have the potential of adding additional 2.01 × 1014 tons/year. These concentrations were considered as environmental menace that could have adverse health challenge of the residents of the host communities. Some technologically driven measures to control and subsequently reduce TEX emission from these refineries were suggested.

The increase in price of the available refined petroleum products for local consumption in Nigeria had led to the emergence of indigenous technology for petroleum refining in some parts of the Niger Delta region. This study, therefore characterized and quantified artisanal refineries’ gaseous emissions for possible air pollutants based on various unit operations involved and evaluated their impacts. It measured the emissions directly from source using E8500 Portable Combustion Analyzer. It also categorized oven sizes/processing capacity of the refineries into various ranges in order to estimate emissions according to processing capacity. The result revealed that; pollutants emission varied significantly between the unit operations and increased with increase in processing capacity. When the emissions were compared with daily limits set by the Environmental Guidelines and Standard for Petroleum Industry in Nigeria (EGASPIN) 2002, the emissions (CO, NOx, and SO2) breached the available set limits. While with the Federal Environmental Protection Agency (FEPA), 1991 set limits for emissions from stationary source; HC and CO breached their limits. SO2 and H2S breached their lower limits but were below the upper limit, while NOx emissions were found within its set limit. The study concluded that, Nigeria Artisanal Petroleum Refineries are sources of air pollution, as they impact the host environment.

This study produces liquid fuel from waste automobile tyres via thermal pyrolysis purposely to investigate the feasibility of replacing conventional fuel with pyrolysis oil in internal combustion engines. Shredded automobile tyres were pyrolysed in an electric-powered pyrolysis reactor and the oil obtained was treated with H2SO4 to remove sludge and to reduce its odour. The treated oil was distilled, and the products obtained have properties similar to gasoline and diesel fuels. The light tyre pyrolysis oil (LTPO) was blended with regular gasoline and the various blends obtained were used in powering an electric generator, and the fuel consumption rate in the generator was observed to reduce with an increase in pyrolysis oil content. Analysis of the exhaust flue gases showed that gasoline-LTPO blends gave a significant reduction in the CO levels. However, the unburnt hydrocarbon (HC) content of the exhaust stream increased with the LTPO content, with the blends containing 60% LTPO having the highest HC level. The conclusion from the study revealed that the tyre pyrolysis oil could possibly replace conventional fuels in internal combustion engines, and the application of the Exhaust Gas Recirculation (EGR) approach could resolve the issues of high HC contents in the exhaust stream.

Major cities in Nigeria has adopted the use of liquefied petroleum gas (LPG) as their main source for domestic cooking, however, this adoption led to different designs of LPG burners in Nigeria market. The emission indices of these burners and their air quality implications are yet to be ascertain. To solve these problems and fill the data gap, laboratory analysis were carried out on 16 conventional LPG burner heads identified in Nigeria market. The emission factors for Carbon monoxide (CO), Oxide of Nitrogen (NOx), Carbon dioxide (CO2), Hydrocarbons (HC) and sulphur dioxide (SO2) on the basis of useful energy delivered were 0.123–21.784 g/MJd, 1.973–32.943 g/MJd, 73.819–147.639 g/MJd, 4.069–171.643 g/MJd and 0–0.1644 g/MJd while the emission rates were 0.000238–0.1125 g/s, 0.0071–0.2 g/s, 0.1083–0.7 g/s, 0.0117–1.2583 g/s and 0–0.000194 g/s respectively. It was observed that results from the study were within the International Organization for Standardization, International Workshop Agreement 11 and World Health Organization indoor air quality guidelines for human protection.

As part of research efforts to investigate the contribution of various anthropogenic activities to local atmospheric pollution load across Nigeria, the study investigated emission of air pollutants from the combustion processes in Lagos mega city. Solid wastes, consumption of fuel wood, and petroleum products were identified as major materials being combusted in Lagos and these materials were quantified based on the information in literature. Annual emissions from the combustion of the quantified materials were estimated using emission factor approach. The total estimated annual contribution of anthropogenic combustion processes to atmospheric loading of PM10, CO, SO2, NOx and VOC were 188.49, 5920.97, 11.24, 348.88 and 4.14 kt/annum, respectively. Emissions from the combustion of solid waste/biomass were identified as a major source of criteria air pollutants in the city because, about 67.5% and 82% of the estimated CO and PM10 emissions, respectively, were generated from the combustion of solid waste/biomass. Also, 81%, 57% and 32% of NOx, SO2 and CO emissions respectively were found to have emanated from combustion of kerosene. These elevated emission levels can be said to have potential impacts on ambient air quality of the study area. The study concluded that immediate mitigating action to reduce release of pollutants from combustion processes should be put in place.

The indoor air quality (IAQ) is paramount to the existence of humans considering the amount of time spent indoors. The indoor pollutant levels may be 100 times the levels outdoors. The indoor pollutants need to be considered to enhance better IAQ. This study determined the emission factors of carbon monoxide (CO) emitted from a standby electricity generator (SEG). It evaluated the impacts of CO concentrations on indoor air quality and identified appropriate ways to mitigate the CO concentrations. The indoor CO concentration was determined by simulating a number of scenarios of SEG operated outdoor using a Simulation Tool Kit for Indoor Air Quality and Inhalation Exposure (IAQX) model. Hourly measurements of mean CO concentrations in the ambient environment and wind speed were conducted for four weeks in four field locations. The emission rate of CO from the standby electricity generator was measured. The CO concentration from SEG was 2.4289 × 104 mg/m3, a very high CO concentration. The CO emission factors were obtained as 2.2366 × 103 kg/m3 of fuel consumed and 9.5411 × 106 kg/hr of activity. High CO concentrations were obtained in microenvironments from the scenarios 1.28 × 104 mg/m3, 4.78 × 103 mg/m3, 4.79 × 104 mg/m3 and 9.58 × 104 mg/m3. The results showed that a high air exchange rate allowed CO concentrations to decay fast while low air exchange rates created an accumulation of CO concentrations indoor.

The impact of particulate matter on the ambient air quality of Landmark University Farm was assessed using deposition fluxes of Trace elements (TEs) in the airshed of the farm. Deposition gauges were employed to collect both dry and wet deposition samples of particulate matter between 2018 and 2019. Elemental compositions of particulates collected during the sampling period were analyzed using Energy Dispersive X-ray Fluorescence Spectroscopy (ED-XRF). The deposition fluxes of crustal and anthropogenic trace elements were also determined using standard methods. Results showed that in dry season, iron has the highest mean concentration (3283.61 mg/kg), while chromium has the lowest (0.023 mg/kg). On the other hand, in wet season, silicon and nickel have the highest and lowest mean concentrations of 159.34 mg/kg and 0.01 mg/kg respectively. Although the concentrations of these metals were higher in the dry season than wet season, there was no statistical significant difference between the mean concentrations of the elements measured in each season of the year (p > 0.05). The compositions of some of the elements in the particulate matters were found to be far above the recommended exposure limits prescribed by OSHA. The study concluded that the elemental composition of particulate matter in the airshed of the University Farm adversely impacts the ambient air quality of the Community.

The acceptance of liquefied petroleum gas (LPG) cookstove has increased across the country in recent years; however, their performance has not been investigated and established. To achieve this, laboratory tests were carried out to evaluate the thermal efficiency, and industrial combustion analyser (E-instrument E8500) was then used to characterize and quantify the air emissions from combustion of conventional LPG cookstoves in the country. The average thermal efficiency for all tested burners was 66.267 ± 7.218% meeting Tier 4 of the International Organization for Standardization, International Workshop Agreement 11. The mean concentration of CO, NOx, HC, and SO2 was in the range of 3–530, 48–810.5, 99–4176, and 0–4,respectively,and the range of CO2 was 1,792–3,592 mg/m3,which were compared with stationary source limit by Federal Ministry of Environment Standard, Nigeria. The toxicity potential of NOx and SO2 was below unity, 25% of the burners tested were below unity for CO, and HC was higher than unity for all tested burners. Most cookstoves met the guidelines for CO, NOx, and SO2. Hence, LPG in Nigeria could serve as a source of energy for cooking.

The presence of carbon in an environment indicates the need for urgent attention on air quality control. Lagos mega city is presently experiencing developmental projects associated with carbon emission potentials, which are yet to be quantified; hence, this study identified and quantified the sources of carbon emission in the Lagos mega city and also determined the quantity of energy consumption capacity for domestic, transportation and industries. Using fuel consumption rate and activity duration, the emissions factors approach were used to determine the quantity of Carbon dioxide (CO2) emission from the household, vehicular operation and electric power generators in the zones. The total CO2 emission from the three major sectors was then used to establish the carbon footprint and annual global warming potential of the mega city. This study reported a CO2 (g) emission of 9.59 × 1013 tons CO2-e per annum for industrial area and 2.41 × 1016 tons CO2-e per annum for non-industrial area. The overall carbon dioxide emission for Lagos Mega City in 2015 was 2.42 × 1016 tons CO2-e per annum which is higher than the value of 1.6 × 1016 tons CO2-e per annum predicted for Lagos BRT CO2 emission, which stands at 66.1% increase from 2014 to 2015 as the reporting periods.

Background This study determined the levels of polycyclic aromatic hydrocarbons (PAHs) in the soil around typical automobile repair workshops in Nigeria. Risk assessment associated with human contact with the soil was carried out using hazard quotient (HQ) and incremental life cancer risk (ILCR) from human unconscious ingestion and dermal contact with the soil. Methods Soil samples were obtained at different automobile workshops in Ado-Ekiti, Western Nigeria. The PAHS in the samples were extracted using dichloromethane and extracts were cleaned up using silica-alumina gel open column chromatography. Analysis of PAHs in the soil was done using a gas chromatograph coupled to a mass selective detector operated on electron ionization mode. Results The results showed the mean PAHs concentration at the sampling locations ranged from 5.58 – 6.4 μg/g and the mean ∑ carcinogenic PAHs was 58.4 μg/g, equivalent to 59.39 % of total PAHs observed. The mean Toxicity equivalence (TEQs) ranged from 0.02 - 6.680 μg/g. Benzo (a) pyrene and dibenzo(a,h)anthracene have the highest toxicity equivalent. The total ILCRs from accidental ingestion and dermal contact in adults were 1 ×10^(-3) and 9.8 ×10^(-5), for adults and children respectively; both are higher than the permissible limit stipulated by the World Health Organization.The HQs obtained are several folds higher than 1. This implies high carcinogenic and non-carcinogenic risks for children and adults. Conclusions The study revealed the levels of PAHs and also revealed the risks associated with human contact with the soil around automobile repair workshops.

Background: This study determined the levels of polycyclic aromatic hydrocarbons (PAHs) in the soil around typical automobile repair workshops in Nigeria. Risk assessment associated with human contact with the soil was carried out using hazard quotient (HQ) and incremental life cancer risk (ILCR) from human unconscious ingestion and dermal contact with the soil. Methods: Soil samples were obtained at different automobile workshops in Ado-Ekiti, Western Nigeria. The PAHS in the samples were extracted using dichloromethane and extracts were cleaned up using silica-alumina gel open column chromatography. Analysis of PAHs in the soil was done using a gas chromatograph coupled to a mass selective detector operated on electron ionization mode. Results: The results showed the mean PAHs concentration at the sampling locations ranged from 5.58 – 6.4 μg/g and the mean ∑ carcinogenic PAHs was 58.4 μg/g, equivalent to 59.39 % of total PAHs observed. The mean Toxicity equivalence (TEQs) ranged from 0.02 - 6.680 μg/g. Benzo (a) pyrene and dibenzo(a,h)anthracene have the highest toxicity equivalent. The total ILCRs from accidental ingestion and dermal contact in adults were 1 ×10^(-3) and 9.8 ×10^(-5) , for adults and children respectively; both are higher than the permissible limit stipulated by the World Health Organization.The HQs obtained are several folds higher than 1. This implies high carcinogenic and non-carcinogenic risks for children and adults. Conclusions: The study revealed the levels of PAHs and also revealed the risks associated with human contact with the soil around automobile repair workshops.

Background: This study determined the levels of polycyclic aromatic hydrocarbons (PAHs) in the soil around typical automobile repair workshops in Nigeria. Risk assessment associated with human contact with the soil was carried out using hazard quotient (HQ) and incremental life cancer risk (ILCR) from human unconscious ingestion and dermal contact with the soil. Methods: Soil samples were obtained at different automobile workshops in Ado-Ekiti, Western Nigeria. The PAHS in the samples were extracted using dichloromethane and extracts were cleaned up using silica-alumina gel open column chromatography. Analysis of PAHs in the soil was done using a gas chromatograph coupled to a mass selective detector operated on electron ionization mode. Results: The results showed the mean PAHs concentration at the sampling locations ranged from 5.58 – 6.4 μg/g and the mean ∑ carcinogenic PAHs was 58.4 μg/g, equivalent to 59.39 % of total PAHs observed. The mean Toxicity equivalence (TEQs) ranged from 0.02 - 6.680 μg/g. Benzo (a) pyrene and dibenzo(a,h)anthracene have the highest toxicity equivalent. The total ILCRs from accidental ingestion and dermal contact in adults were 1 ×10^(-3) and 9.8 ×10^(-5) , for adults and children respectively; both are higher than the permissible limit stipulated by the World Health Organization.The HQs obtained are several folds higher than 1. This implies high carcinogenic and non-carcinogenic risks for children and adults. Conclusions: The study revealed the levels of PAHs and also revealed the risks associated with human contact with the soil around automobile repair workshops.