A Survey of Trace Metals in Vegetation, Soil and Lower Animal Along Some Selected Major Roads in Metropolitan City of Lagos

The concentration of trace metals (Cd, Cu, Pb and Zn) in a total of 144 samples of grass, soil and lower animal (earthworm, Lybrodrilus violaceous) were collected and analysed for their metallic content. Levels of cadmium ranged from 0.01–0.07 g g^–1; 0.01–0.12 g g^–1 and from trace–0.05 g g^–1 dry weight for plant, soil and animal samples respectively. Mean concentration of copper ranged 0.10–1.48 g g^–1; 0.10–2.90 g g^–1 and 0.01–0.08 g g^–1 for samples in similar order as above. The levels of Pb varied from 0.01–0.14 g g^–1; 0.02–0.23 g g^–1 and from trace–0.07 g g^–1 while that of Zn ranged from 0.19–1.80 g g^–1; 0.51–3.35 g g^–1and 0.01–0.08 g g^–1 also in the same order of samples as mentioned above. Levels of metals in soil samples were higher than the background levels with the exception of Zn but lower than European Union (EU) limits. The results generally revealed the presence of metals in plant and animal samples and metal dynamics up the food chain is highly possible. Acceptable recoveries of the spiking experiment validate the experimental protocol.     

Bioindicator organisms: Heavy metal pollution evaluation in the Ionian Sea (Mediterranean Sea—Italy)

Trace metal concentrations of mercury, cadmium, lead and chromium in Patella caerulea, and Mullus barbatus were investigated to provide information on pollution of Ionian Sea, since these metals have the highest toxic potential. High chromium levels (0.47–0.97 g g^–1 ww) were registered in limpet samples collected from two station near the Gulf of Taranto, while elevated concentration of mercury (0.31–1.50 g g^–1 ww) were found in mullet specimens from Sicily. The metal concentrations recorded at the clean stations may be considered as useful background levels to which to refer for comparison within the Mediterranean area. On the contrary, the high levels of chromium and mercury found respectively in the areas near the Gulf of Taranto and at Capo Passero being of concern in terms of environmental health need frequent monitoring.     

Long term monitoring of pollutants in eggs of Yellow-legged Herring Gull from Capraia island (Tuscan Archipelago)

Chlorinated hydrocarbons (hexachlorobenzene, lindane, ppDDE, polychlorinated biphenyls) and trace elements (Hg, Se, Cd, Pb) were determined in eggs of Yellow-legged Herring Gull (Larus cachinnans) collected in an island of the Tyrrhenian Sea during the period 1981–1986. PCBs levels vary on the average between 30.4g g^–1 d.w. in 1981 to 56.1 g g^–1 d.w. in 1983. The capillary chromatograms revealed the presence of about 30 somers of PCBs without significant variations in the eggs of the same year; more than 50% of the residues is made up only three isomers: the 22'44'55', the 22'344'5' and the 22'344'55'. Average DDE residues were 7–8 times lower than those of PCBs and declined during the period (from 9.2 g g^–1 d.w. in 1981 to 4.5 g g^–1 d.w. in 1986). Cadmium and lead are present in low concentrations. The average levels of mercury and selenium are around 2–2.5 g g^–1 d.w., and a cumulative correlation, on a molar basis, exists between these two elements.     

Organochlorines and selenium in California night-heron and egret eggs

Exceptionally high concentrations of DDE were found in black-crowned night-heron (Nycticorax nycticorax) (geometric mean 8.62 g g^–1 wet wt.) and great egret (Casmerodius albus) (24.0 g g^–1) eggs collected from the Imperial Valley (Salton Sea), California in 1985. DDE concentrations in 14 of the 87 (16%) randomly selected night-heron eggs from six colonies (two in San Francisco Bay, three in the San Joaquin Valley, and one at Salton Sea) were higher than those associated with reduced reproductive success of night-herons (8 g g^–1). In addition, mean shell thickness of night-heron eggs collected from the San Joaquin Valley and from San Francisco Bay during 1982–1984 was significantly less than pre-DDT thickness and was negatively correlated (r=–0.50, n=75, P<0.0001) with DDE concentration. Mean selenium concentration in night-heron eggs from Salton Sea (1.10 g g^–1) was significantly higher than in eggs from three locations in the San Joaquin Valley, and in egret eggs from Salton Sea.     

Atrazine and Alachlor Inputs to Surface and Ground Waters in Irrigated Corn Cultivation Areas of Castilla-Leon Region, Spain

The inputs of atrazine and alachlor herbicides to surface and ground waters from irrigated areas dedicated to corn cultivation in the Castilla-León (C-L) region (Spain) as related to the application of both herbicides were studied. Enzyme-linked immunosorbent assays (ELISA) were used for monitoring the atrazine and alachlor concentrations in 98 water samples taken from these areas. Seventy-nine of the samples were of ground waters and 19 were of surface waters. The concentration ranges of the herbicides detected in the study period (October 1997–October 1998) were 0.04–25.3 g L^–1 in the surface waters and 0.04–3.45 g L^–1 in the ground waters for atrazine, and 0.06–31.9 g L^–1 in the surface waters and 0.05–4.85 g L^–1 in the ground waters in the case of alachlor. The highly significant correlation observed between the concentrations of both herbicides in the surface waters (r = 0.89, p < 0.001) pointed to a parallel transport of atrazine and alachlor to these waters. A study was made of the temporal evolution of the concentrations of both herbicides, and it was found a maximum recharge of atrazine in the ground waters for April 1998 and of alachlor in October 1997 and October 1998. The temporal evolution of the concentrations of both herbicides in surface waters was parallel. The highly significant correlations observed between atrazine concentrations determined by ELISA and by HPLC (r = 0.92, p < 0.001) and between alachlor concentrations also determined by both methods (r = 0.96, p < 0.001) confirmed the usefulness of ELISA for monitoring both herbicides in an elevated number of samples. Using HPLC, the presence in some waters of the alachlor ethanesulfonate (ESA) metabolite was found at a concentration range of 0.52–4.01 g L^–1. However the interference of ESA in the determination of alachlor by ELISA was negligible. The inputs of atrazine and alachlor to waters found in this study, especially the inputs to ground waters, could pose a risk for human health considering that some waters, though sporadically, are even used for human consumption.     

Environmental Contaminants in Blood, Hair, and Tissues of Ocelots from the Lower Rio Grande Valley, Texas, 1986–1997

The ocelot (Felis pardalis) isan endangered neotropical cat distributed within asmall range in the Lower Rio Grande Valley (LRGV), inTexas, U.S.A. Studies of the impacts of environmentalcontaminants in wild cats are few. Approximately onefourth of the estimated population (about 100) ofocelots in the LRGV was sampled to evaluate theimpacts of chlorinated pesticides, polychlorinatedbiphenyls, and trace elements on the population. Hairwas collected from 32 ocelots trapped between 1986–1992,and blood was collected from 20 ocelots trappedbetween 1993–1997. A few blood samples were obtainedfrom individuals recaptured two or three times. Tissue samples from 4 road-killed ocelots were alsoanalyzed. DDE, PCBs, and Hg were some of the mostcommon contaminants detected in hair and blood. MeanHg levels in hair ranged from 0.5 to 1.25 g g^-1 dw,Se from 1.5 to 3.48 g g^-1 dw, and Pb from 0.56 to26.8 g g^-1 dw. Mean DDE concentrations in plasma ranged from 0.005 g g^-1 ww to 0.153 g g^-1 ww, and PCBs ranged from 0.006 g g^-1 ww to 0.092 g g^-1 ww. Mean Hg levels in red blood cells rangedfrom 0.056 g g^-1 dw to 0.25 g g^-1 dw. Concentrations of DDE, PCBs, or Hg, did not increasesignificantly with age, although the highestconcentrations of DDE and Hg were found in olderanimals. Overall, concentrations of DDE, PCBs, and Hgwere low and at levels that currently do not pose anythreat to health or survival of the ocelot. This isfurther supported by good reproduction of the ocelotin the LRGV, where adult females averaged about 1.5kittens/litter. Thus, it seems that the current majorthreat to recovery of the ocelot in the LRGV may behabitat loss, although potential impacts of newgeneration pesticides, such as organophosphorus andcarbamate insecticides need further study.     

Beryllium Concentrations in Ambient Air and Its Source Identification

Beryllium concentrations in atmospheric particulate and soil samples in and around a Beryllium Processing Facility (BPF) have been measured. The mean air concentration level of beryllium in and around the fence line of the BPF is 0.48 ± 0.43 ng m^-3 (n = 397) and is mostly influenced by diurnaland seasonal changes. The observed air concentration levelswere well below the prescribed ambient air quality (AAQ)standard of 10 ng m^-3. The soil concentration levels ofberyllium in the study area were found to be in the range of 1.42–2.75 g g^-1. The mass median aerodynamic diameter (MMAD)of beryllium aerosols in ambient air was found to be 6.9 m.Source identification using the Enrichment Factor (EF) approachindicates soil as the predominant contributory source for air concentrations at the site.     

Response of Mercury Contamination in Fish to Decreased Aqueous Concentrations and Loading of Inorganic Mercury in a Small Stream

Approximately 250 000 kg of mercury was lost towater and soils at the U.S. Dept. of Energy Y-12 Plantin Oak Ridge, Tennessee in the 1950s and early 1960s. A creek originating within the plant receivedcontinuous inputs of waterborne mercury, predominantlyas dissolved inorganic mercury, from groundwater,streambed contamination, and sump and process waterdischarges to the contaminated storm sewer network.These produce aqueous total mercury concentrations of1–2 g L^-1 in the upper reaches of the stream,decreasing to about 0.1–0.2 g L^-1 in its lowerreaches. A program to reduce mercury concentrationsin the creek identified specific sources (buildingsumps, contaminated springwater seeps, foundationdrains, and contaminated piping) and rerouted wateraround contaminated portions of the drain system orcollected and treated mercury-contaminated waterbefore discharging it. As a result, waterbornemercury concentrations in the creek and total mercuryloading were reduced from 1.8 g L^-1 to0.6 g L^-1 and 100 to 20 g d^-1, respectively, in the last 5 yr.Mean mercury concentrations in fish nearest sourceareas in the creek headwaters decreased at roughly thesame rate as waterborne total mercury concentrationsover the past five years, but at the facility boundarydownstream the decline in mercury bioaccumulation wasmuch less. At sites 5–15 km farther downstream, nodecrease was evident. Dissolved methylmercury tendedto increase with distance downstream in a patterninverse to that noted for its dissolved inorganicmercury precursor.Improvements in water quality and modification ofweirs to allow the passage of fish have resulted inthe establishment of large populations of fish inmercury-contaminated headwater areas previously devoidof fish. It may be that the accumulation, retention,and eventual downstream transport of this reservoir ofbiologically incorporated methylmercury has acted tobuffer against expected reductions in mercury in fishat downstream sites.     

Measurement of atmospheric concentrations of common household pesticides: A pilot study

Air concentrations of 28 of the most commonly used household pesticides were measured inside nine homes in Jacksonville, Florida, and compared with corresponding outdoor levels. The households selected were sorted into three categories according to the degree of pesticide indoor usage. Personal air monitoring was also performed on one resident of each household by means of a portable sampler, which was kept with the person at all times. Five of the pesticides were found in the air inside of the majority of the homes at concentrations as high as 15 gm^–3 (average concentrations, 12 ngm^–3 to 2.4 gm^–3). Indoor levels were generally one to two ordrrs of magnitude higher than surrounding outdoor air levels and personal air measurements were within ± 50% of corresponding indoor values. All samples were collected over 24-hr periods on polyurethane foam and analyzed by capillary colum gas chromatography with mass spectrometric and/or electron capture detection.     

Behaviour and fluxes of trace and toxic elements in creek sediment near Mumbai,India

Studies on marine sediments are extremely important since they act as ultimate sink of anthropogenic pollutants. The present study was conducted near Mumbai city of India to understand andassess the behaviour and fluxes of trace and toxic elements increek sediment. Seven sediment core samples were collected andanalysed for trace and toxic elements such as Fe, Cu, Pb, Zn, Rb and Sr in different sections of the core using EDXRF technique. The fluxes of the elements in each section of the core were calculated using the mass sedimentation rates derivedfrom ²¹⁰Pb dating technique and the sediment density at each location. The estimated depositional fluxes of Fe, Rb and Sr in Zone-1 and Zone-3 are in the ranges of 0.4–0.5% cm^-2yr^-1; 4–6 g cm^-2 yr^-1 and 10–20 g cm^-2 yr^-1 respectively, where as they were about 3–4 times higher in zone-2 for the same elements. The depositionalfluxes of elements Cu (40–60 g cm^-2 yr^-1), Zn (35–43 g cm^-2 yr^-1) and Pb (6–12 g cm^-2 yr^-1) were also found to be higher in zone-2 compared tozone-1 and zone-3 which can be attributed to the release from thenewly developed chemical zone of Thane-Belapur industrial belt.     

Determination of Cadmium and Lead in Different Cigarette Brands in Jordan

Cadmium (Cd) and lead (Pb) concentrations in different cigarette brands sold and/or produced in Jordan were determined by graphite furnace atomic absorption spectrometry (GF-AAS). Average levels of Cd and Pb in different cigarette brands in Jordan were 2.64 and 2.67 g g^{– 1} (DW), respectively. The results obtained in this study estimate the average quantity of Cd inhaled from smoking one packet of 20 cigarettes to be in the range of 3.65–7.30 g. Results suggest that the quantity of Pb inhaled of smoking one packet of 20 cigarettes, is estimated to be 0.74–2.22 g. The concentrations of Cd and Pb in cigarettes were significantly different between cigarette brands tested. Our results were compared with other worldwide studies.     

Arsenic uptake and loss in the American oyster,Crassostrea virginica

In addition to a control Crassostrea virginica was treated with 3 and 5 g As kg^p-1 for 16 wks at ambient seawater salinity and temperature to determine the potential of C. virginica as an indicator of arsenic pollution. Prior to spawning, as much as 10.3±1.5, 12.7±2.7, and 14.1±3.7 g As g^p-1 dry weight were accumulated in the total soft parts of oysters after treatment with ambient (control), 3 and 5 g As kg^-1, respectively. Immediately after spawning, an increase in tissue arsenic concentration was observed in all treatments up to week 12, after which a decrease in tissue arsenic concentrations occurred despite continuous addition of arsenic to the seawater. During the uptake period, a significant inverse relationship existed between dry weight and tissue arsenic concentration, whereas a significant direct relationship was apparent between dry weight and tissue content. Arsenic concentration in the total soft parts is not significantly related to seawater arsenic concentration over the range of concentrations used in this study. In all three treatments, arsenic uptake as concentration (g g^p-1) is not a significant linear function of time. Weight loss was significant but gradual during the first 16 wks of treatment and did not change significantly during the depuration period (wks 17–25). Tissue arsenic concentrations increased significantly in oysters from all three treatments during the depuration period. Generally, arsenic body burdens increased with increases in phytoplankton concentration and it appears that food contributes more to arsenic uptake than seawater arsenic concentrations. Since a relationship between tissue arsenic concentration and seawater arsenic concentration does not appear to exist, C. virginica would not be a good biological indicator of arsenic concentration in its environment.     

Heavy Metal Concentrations in and Around Households Near a Secondary Lead Smelter

Housedusts and garden soils were sampled in 14 houses in the vicinity of a secondary Pb smelter and analysed for concentrations of Pb, Zn, Cu, Cd, As, and Hg. Sixty-one topsoil samples were also taken from a 2 km² grid covering the smelter grounds and surrounding residential areas and analysed for concentrations of Pb, Zn, Cd and Cu. Contour maps generated from the grid data indicate significant contamination in the area (maximum Pb concentration 58 500 g g^-1), particularly down-wind of the smelter grounds. A geometric mean Pb concentration of 2225 g g^-1 was recorded in garden soil and similarly elevated levels were recorded for Zn, Cd, As and Sb. In housedusts, a geometric mean Pb concentration of 1668 g g^-1 was observed. Whilst housedust metal concentrations were generally elevated, compared to other urban or residential areas, there appears to be a large degree of attenuation of the metals between the exterior and interior environments of the homes studied. A significant correlation was not recorded between metal concentrations of garden soils and housedusts. There were significant correlations for: distance from the smelter against garden soil metal concentrations; garden soil metal concentrations against each other; housedust metal concentrations against each other; and house age against garden soil metal concentrations.     

Effect of Common Pesticides Used in the Niger Delta Basin of Southern Nigeria on Soil Microbial Populations

The effects of eleven pesticides on the populations of bacteria, actinomycetes, fungi and protozoa was investigated by treating a garden soil with their recommended rates. The microbial populations were estimated using the standard plate-count technique. Of the ll pesticides investigated, phenylmercuric acetate (agrosan) at 50 g g^-1 inhibited bacterial density the most, i.e. from 4,600,000 to 220 cells g^-1. The pesticides were Pentachloronitrobenzene (PCNB), tetramethylmethylthiuram disulphide (thiram),1- naphthylmethylcarbamate (Vetox 85), 1,2,3,4,5,6-hexachlorocyclohexane (Gammalin 20), phenylmercuric acetate (Agrosan), tetrachloroterephthalic acid (Dacthal), 4-nitrophenyl –2-nitro-4-trifluoromethylphenyl ether (Preforan), 2-ethyl-6-methyl –N-2-methoxy –1-methyl ethyl-chloroacetanide (Dual), Benlate, Brestan and Gramoxone. Pentachloronitrobenzene (PCNB) at 240,000 g g^-1 reduced bacterial population from 4,600,000 to 2,100 cells g^-1, whereas tetramethylthiuram disulphide (thiram) at 100 g g^-1 suppressed it by 2 log orders of magnitude. Soil application of 1-naphthylmethylcarbamate (Vetox 85) at 100 g g^-1 and 1,2,3,4,5,6,-hexachlorocyclohexane (Gamalin 20) at 1,300 g g^-1 repressed the bacterial numbers by 2 log orders of magnitude each. Pentachloronitrobenzene reduced the actinomycetes density from 340,000 to 320 cells g^-1 and completely eliminated all fungal and protozoan propagules from the soil. The Gammalin 20 completely wiped out all the fungi, whereas phenylmercuric acetate totally eliminated all the protozoa and reduced the fungal population from 34,000 to 60 cells g^-1. In general, protozoa and fungi were more susceptible to fungicides than bacteria and actinomycetes. Pentachloronitrobenzene, 1,2,3,4,5,6,-hexachlorocyclohexane and phenylmercuric acetate were toxic particularly to soil microorganisms, whereas the herbicides dacthal, Preforan and Dual were quite harmless in soil at application rates of 0.1, 0.06 and 0.02 g g^-1 respectively.     

Heavy Metals and Chlorinated Hydrocarbon Concentrations in the Red Fox in Relation to Some Biological Paramaters

Heavy metals and organochlorine contamination were analyzed in tissues of red foxes (Vulpes vulpes) from the Province of Siena (central Italy). Mercury (Hg), cadmium (Cd) and lead (Pb) concentrations were assessed in liver tissues and the data were analyzed for differences in relation to sex and age. Overall Hg, Cd and Pb mean values were 0.16, 0.62 and 0.64 g g^_1 d.w., respectively. HCB, DDT and PCB concentrations were assayed in fatty tissues and muscle. The highest levels of those pollutants were found in muscle (0.47, 1.16 and 20.2 g g^_1 lipid basis of HCB, DDTs and PCBs respectively), rather than in fat (0.23, 0.49 and 7.2 g g^_1 l.b. of HCB, DDTs and PCBs respectively). Pollutant accumulation was analyzed in relation to sex, age and sexual maturity of females.     

Trace Metal Concentration in Roadside Surface Soil and Tree Back: A Measurement of Local Atmospheric Pollution in Abuja, Nigeria

Cadmium, copper, lead, nickel and zinc concentrations were analysed by atomic absorption spectrophotometry in surface soil and tree bark from different districts of Abuja, Nigeria, in order to determine the atmospheric trace metal input in the area.Elevated concentrations of some of the studied metals were observed in the soil and tree bark samples from the commercial/high traffic areas of the city compared to backgroundvalues. In soil samples, the average concentration of the metals were 0.6±0.4, 18.0±4.0, 281±39, 16±4 and66±23 g g^-1 dry weight for Cd, Cu, Pb, Ni and Zn, respectively, whilst the average concentrations in tree bark were 0.3±0.2, 12±4, 133±32, 13±3 and 61±10 g g^-1 dry weight for Cd, Cu, Pb, Ni and Zn, respectively. The trend in trace metal levels suggested that automobile emissions are a major source of these metals as the highest concentrations of Pb and Zn were recorded in the commercial areas of the city known for their high traffic densities. The levels of metal in the study area were relativelylow compared to levels found in some larger and older cities in various countries worldwide.     

Distribution of heavy metals in plants and fish of the Yamuna river (India)

The distribution of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) in the plants and fish of Yamuna river from Delhi to Allahabad, a distance of about 840 km, at five sampling stations was determined in the year 1981. The results have shown wide variations in the heavy metal levels from one sampling station to the other. The concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in the plants (Eicchornia crassipes) were found to be 0.02–0.12, 2.7–21.3, 4.6–64.8, 9.8–114.0, 193.0–1835.0, 380.0–1443.0, 4.4–83.0, 4.8–30.2, and 22.1–356.5 g g^-1 respectively whereas in the fish (Heteropnuestes fossilis) were found to be ND-0.40, 2.3–13.7, 3.7–26.9, 8.33–58.1, 278.3–1108.0, 81.3–213.8, 2.8–32.7, 1.4–12.8 and 101.8–364.8 gg^-1 respectively on dry weight basis.     

Atmospheric Dust Loads and Their Elemental Composition at a Background Site in India

Air particulate samples collected during 1995–96 ata background site situated on the east coast of Thar Desert inRajsthan State of India were analysed for atmospheric dustloads (Suspended Particulate Matter) and elemental composition.The values of SPM ranged from 9 g M^-3 to 97g M^-3 with an average of 43 g M^-3 except a fewepisodic values, which were 3 to 5 times higher than the averageduring summer months. The results for elemental composition ofthe particulate samples showed that the concentrations ofanthropogenic toxic trace elements viz. Br, Cr, Pb, Sb, Se and Znare lower by a factor of 2 to 10 as compared to urban areas. Thehigh enrichment factors for anthropogenic elements viz. Br, Pb,Sb and Zn show an input from coal/wood fuel burning andvehicular pollution at the sampling site. The depletion of Si inSPM samples shows long distance transport of dust to the samplingsite.     

Monitoring dissolved copper concentrations in Chesapeake Bay,U.S.A.

Dissolved copper and selected water chemistry parameters were monitored for 11 months in Chesapeake Bay, U.S.A. Dissolved copper concentrations in four recreational marinas, a large harbor, two major river systems, and a heavily used shipping canal ranged from below detectable levels to 80 g L^-1 (\-X=11.7 g L^-1). Dissolved copper was detected >91% of the time at five locations. Lowest copper concentrations were found in Potomac River, Baltimore Harbor, Pier One Marina, and C & D Canal (\-X=6–10 g L^-1; slightly higher levels of dissolved copper were found in Choptank River (\-X=12 g L^-1). Highest levels of copper were detected in Port Annapolis, Hartge, and Piney Narrows Marinas (\-X=13–18 g L^-1), with the highest values observed in the study (70 and 80 g L^-1) found in two of these marinas. Copper in the three marinas with highest dissolved copper levels could have been toxic to some of the more sensitive aquatic species. Intensive study of one marina indicated that a likely source of dissolved copper was the recreational boats housed in the marina.     

Roadside Concentration of Gaseous and Particulate Matter Pollutants and Risk Assessment in Dar-Es-Salaam, Tanzania

This study used manual air sampling method to assess the contribution of road traffic to air pollution level in Dar-es-Salaam City, Tanzania. Samples were collected from 11 different sites. Parameters measured were: sulphur dioxide using pararosaniline method, nitrogen dioxide using saltzman method, particulate matter and particulate lead using filtration method and atomic absorption spectrometric method, respectively. Results showed that hourly average sulphur dioxide concentration range from 127 to 1385 g/m³. The measured values of sulphur dioxide were above the recommended WHO guidelines with an hourly objective value of 350 g/m³ at 87% of the sampling sites. The hourly average nitrogen dioxide concentration ranged from 18 to 53 g/m³. The maximum hourly nitrogen dioxide concentration at 53 g/m³ was below the WHO guideline value of 200 g/m³. The hourly average suspended particulate matter (SPM) ranged from 98 to 1161 g/m³, exceeding the recommended value of 230 g/m³ by WHO at 87% of the sampling sites. The hourly average lead concentration was found to range from 0.60 to 25.6 g/m³, exceeding again the WHO guideline value of 1.5 g/m³at 83% of the sampling sites. Results predicted by Gaussian model when compared with the measured values were found to have a correlation coefficient of 0.8, signifying a good correlation. The risk assessment was undertaken considering the people who spend a significant portion of their time near the roads, such as the Uhuru primary school pupils and the adult population who reside by the roadside. The unit risk realised was 18.2 × 10^–6 for adult population and 2.2 × 10^–6 for pupils, both scenarios showing risk higher than the United Sates of America Environmental Protection Agency (USEPA) acceptable limit of 1× 10^–6. Considering the magnitude of the problem at hand, this study recommends an introduction of mandatory emission tests of SPM, lead and sulphur dioxide (SO₂). The study further recommends the introduction of continuous and/or regular air quality monitoring and the use non-leaded petrol in Tanzania.