Numerous particulates are released from the dumpsites in Owerri metropolis and later dispersed to other areas in the environment where they cause adverse health challenges to the inhabitants. To analyze the PM concentrations, field measurements were carried out at seven major dumpsites in Owerri Metropolis. Estimates of the possible health risks as the result of exposure to airborne particulate matter (PM2.5, PM10, etc.) were performed using the United States Environmental Protection Agency (USEPA) human health risk assessment framework. A scenario assessment approach in which normal exposure and worst-case scenario were adopted for acute and chronic exposure periods for infants, children, and adults were carried out. The concentrations of PM2.5 which ranged from 122.30–501.76 μg/m3 at the dumpsites exceeded the WHO 24 hr annual mean maximum exposure limit. The Nigerian National Ambient Air Quality Standard allowable limit for PM10 was exceeded by most of the dumpsites. Hazard quotient > 1 was exceeded for PM 2.5 by nearly all dumpsites and is therefore likely to cause health challenges to people in the vicinity of the dumpsites. The results showed that under monthly conditions, both PM2.5 and PM10 concentration levels at the dumpsites have the potential to cause adverse health effects for infants, children, and adults on acute or chronic bases. Actions should be taken to regulate such PM exposure and to raise public awareness for the inhabitants of the affected areas. In conclusion, regular monitoring is therefore recommended to decrease the ambient particulate matter (PM) concentrations in the study area.
Air contaminants are generated in the dumpsites areas due to numerous reasons like open burning, uncaptured landfill gases, gases from the decomposition of natural matter, dust from poorly covered landfills, etc. [
The gradual and consistent environmental pollution, the poor ambient air quality in the cities as a result of industrialization and urbanization in addition to the dynamic processes of atmospheric radiation, transmission, dispersion, emission, and transformation influences the distribution and negative health impact of particulates [
The average human being breathes about 15 m3 of air every day including fine PM pollutants which causes serious health problems such as asthma, nose and throat irritation, irritation of the lungs, risk of cardiac arrest, bronchitis, pneumonia, allergies, adverse neurological conditions, reproductive defects, cancer, and even death [
The ecological and human risk assessment techniques are commonly employed to evaluate the effects of PMs on the human body. The human health risk assessment is a technique in which the extent of exposure to PM contaminants together with the life cycle impact assessment (LCIA) method is usually analyzed. [
Imo State, Nigeria which is given by the geographical coordinates defined by longitudes 6° 40′ 02″− 7° 21′ 05″E and latitudes 5° 10′ 05″− 5° 56′ 12″N is predominantly a lowland located to the east of the Niger in southeastern Nigeria and covers a total landmass of approximately 5100 km2 as shown in
The EXTECH Video Particulate Counter is a multi-parameter digital anemometer (Model no: VPC300) that was used for measuring the particulate matter concentrations across the seven (7) different locations. The instrument was tested, calibrated, and certified by FLIR commercial systems Inc., Nashua, the USA on 02/11/2018. The instrument has six standard particle counter channels which measures the 0.3, 0.5, 1.0, 2.5, 5.0 and 10 μm. The equipment mode usually shows the differential, cumulative, and concentration modes. Quality control was achieved by calibrating using the DM-001 procedure earlier described by the National Institute of Standards [
where
q = flow rate in liters per minutes
T = time of sampling in minutes
Wn = mass change of the filter
V(m3) = volume of air sample
The particulate matter data were obtained from the sampling procedure described above. The arithmetic means, median, standard deviation, and coefficient of covariance were calculated from the data using Microsoft Excel 2010 and origin 64-bit 9.0 software. GIS/GPS and MATLAB 7.9 software were used in generating the general finite line model interpretations and spatial contouring of the data. The influence of meteorological parameters (wind speed, wind chill, temperature, relative humidity, dew point, and wind direction) on PM (0.3, 0.5, 1.0, 2.5, 5.0, 10.0) measurements were also investigated. The data acquired with GPS were fed into the Arc GIS 9.3 software version, while the plot of coordinates against the seven locations in the Owerri metropolis was determined using MATLAB 7.9 version software [
The HHRA is a procedure that involves the inclusion of possible negative effects arising from human exposure to toxic substances. The HHRA that was used in this study comprises of four components: Hazard Identification (HI), Dose-Response Assessment (DRA), Exposure Assessment (EA), and Risk Characterization (RC).
The hazard identification of respiratory suspended particulate matter (PM 2.5) and suspended particulate matter (PM10) as harmful and potential health risks was outlined and discussed in key existing pieces of literature [
The exposure-response assessment (DRA) was performed by determining the PM concentration with respect to time activity data es expressed in the equation below.
The
EA is a tool that identifies the population exposed to the hazard, magnitude, and exposure duration to the hazard. The current study assumed that the inhalation route is the major route of exposure to the measured pollutants at the dumpsites. Furthermore, the present study utilized a scenario assessment method for normal average exposure (24-hr-immediate) and worst-case scenario (chronic-annual) exposure periods, as well as the normal acute 1 hr. exposure periods. These referenced doses and their calculations are shown in
For non-carcinogenic pollutants exposure, the acute exposure rate equation is used as shown below [
Where AHD is the average hourly dose for inhalation (μg/kg/hour), C is the concentration of the chemical (μg/m3), IR is the inhalation rate (m3/hour), and BW is the body weight (kg).
For exposure to non-carcinogenic pollutants, the chronic exposure rate is given in
Where ADD is the average daily dose of the chemical of interest (μg/kg/day),
Exposure duration ED was calculated as:
Also, the difference is that exposure duration (ED) is obtained when duration exposure (DE) in years is converted to days by multiplying DE with exposure frequency (EF) and exposure time (ET)
Where ET is the recorded exposure time (hour/day), EF is the exposure frequency (days/year), and DE is the duration of exposure (year). The standards are shown in
The hazard quotient (HQ) shows the probability of adverse health effects occurring among healthy and sensitive groups of people. HQ is given as where REL is the dose at which significant adverse health effects occur in exposed groups compared with the unexposed group. Reference exposure level (REL) was taken from the office of the environmental health hazard assessment (OEHHA) and the RELs used are presented in
An HQ of 1.0 is considered to be the benchmark of safety. HQ that is < 1.0 indicates a negligible risk; that is, the pollutant under scrutiny is not likely to induce adverse health effects, even to a sensitive individual. HQ >1.0 indicates that there may be some risks to sensitive individuals as a result of exposure [
From
The use of a private car was commonly used by adults to bin their wastes. In the mornings, a stop by is made and the waste is binned. During weekends they take a little more time to carefully dispose of their wastes. Hence, children and adults’ exposure to particulate matter pollutants occurred at different levels at the dumpsites. The graphical plot of the time spent by the various groups close to the dumpsites is shown by the box and whiskers plot (
Based on the data obtained from the sampling locations, the different concentrations of PM were determined according to the sizes and diameter of the particulate matter. From
The concentrations of PM2.5 ranged from 122.30–501.76 μg/m3 at OAM and NNR dumpsites in August. Furthermore, maximum PM 2.5 Concentrations was 1662.98 μg/m3 at OOR while the lowest was at OAM dumpsite with a concentration of 119.17 μg/m3. This thus revealed that the PM concentration levels at the dumpsites exceeded the WHO 24hr annual mean maximum exposure limit. On the other hand, PM10 concentration levels in January and August did not exceed the 24hr WHO exposure limits [
The HQ from the health risk characterization from the exposure to PM10 and PM2.5 is provided thus indicating the green baseline of HQ = 1 as shown in
PM2.5 exceeded the WHO 24hr annual mean maximum exposure limit. On the other hand, PM10 concentration levels in January and August did not exceed the 24hr WHO exposure limits. The acute and chronic PM2.5 and PM10 concentrations recorded in January and August did not pose any health risk challenges. However, the PM2.5 HQ levels in August are a major concern while infants are likely to experience health challenges due to exposure to PM10 in January. Therefore, the data thus revealed that PM2.5 and PM10 levels may cause health-related challenges in Owerri Metropolis. Future campaigns should be encouraged, and findings could guide the development of improved protocols for waste disposal in Owerri metropolis and environs.
Special thanks go to the Management of the Federal University of Technology, Owerri for the support given in the course of this research work. This work was sponsored by the TETFUND IBR 2021 of the Federal University of Technology, Owerri, Nigeria
The authors declare that no conflict of interest exists.
AIO: Conceptualization, Methodology, Software, Data Curation, Visualization, Investigation, Writing - Original Draft Writing-Reviewing and Editing; CZA: Conceptualization, Methodology, Software, Visualization, Investigation, Supervision, Writing - Reviewing and Editing; COA: Conceptualization, Methodology, Software, Data Curation, Writing - Original Draft, Supervision; AUN: Conceptualization, Methodology, Software, Visualization, Writing-Original Draft, Writing-Reviewing and Editing; FCI: Conceptualization, Methodology, Software, Data Curation, Writing - Original Draft, Supervision; AWV: Conceptualization, Methodology, Software, Data Curation, Investigation, Supervision; ICC: Conceptualization, Methodology, Software, Data Curation, Visualization, Supervision.
Google map of the study area showing:(a) Nigeria; (b) Imo State; (c) Seven dumpsite locations in Owerri.
Box and whiskers plot of the time spent by residents at dumpsites.
PM concentration levels across the seven dumpsites in the metropolis: (a) Month of January; (b) Month of August.
Calculated hazard quotient (HQ) of measured particulate matter: (a) PM2.5; (b) PM2.5 in August; (c) PM10 in January; (d) PM10 in August.
Spatial plots of the six metrological parameters determined in Owerri metropolis in August during rains.
Geo-referenced coordinates and locations for 7 study sites in Owerri metropolis.
S/N | Dumpsite locations | Code | Longitude | Latitude | Elevation |
---|---|---|---|---|---|
1 | Nekede/Naze FUTO road | NNR | 007°01′ 381″E | 05°26 303″N | 63 |
2 | Old Aba Road | OAM | 007°02′ 506″E | 05°28 673″N | 77 |
3 | Umuawuka Mbaoma Emii | UMR | 007°06′ 042″E | 05°27 400″N | 109 |
4 | Ezeogba Emekuku | EER | 007°01′ 381″E | 05°26 303″N | 63 |
5 | Trans-Egbu Road | TER | 007°02′ 506″E | 05°28 673″N | 77 |
6 | Owerri-Onitsha Road | OOR | 007°06′ 042″E | 05°27 400″N | 109 |
7 | Afor Egbu Owerri | AER | 007°04′ 292″E | 05°28 257″N | 89 |
NNR: Nekede/Naze road; O: Old/Aba road; UMR: Umuawuka/Mbaoma road; EER: Ezeogba/Emekuku road; TER: Trans/Egbu road; OOR: Owerri/Onitsha road; AER: Afor/Egbu road.
US Environmental Protection Agency standards for human health risk assessment parameters.
Exposure frequency, exposure duration, and averaging time for different exposure groups | |||||
---|---|---|---|---|---|
Exposed group | EF (days/year) | DE (year) | AT (days | ||
Infant (0–1 year) | 350 | 1 | 365 (1X365) | ||
Child (6–12 years) | 350 | 12 | 4380 (12x365) | ||
Adult (19–75 years) | 350 | 52 | 18,980 (52X365) | ||
Adapted from [ | |||||
Intermediate (Exposure hours) | Chronic (Exposure hours) | ||||
Exposed group | Acute | Normal | Worst case | Normal | Worst case |
Infant (0–1 year) | 1 | 1 | 24 | 14.6 (350/24)X1 | 350 (1 X 350) |
Child (6–12 years) | 1 | 6 | 24 | 1050.0 (4200/24)X6) | 4200 (12 X 350) |
Adult (19–75 years) | 1 | 3 | 24 | 1312.5 (10500/24)X3 | 10500 (30 X 350) |
Adapted from [ | |||||
Mean inhalation rate (m3/hour) | |||||
Exposed group | Acute exposure | Chronic exposure | Mean body weight | ||
Infant (0–1 year) | 0.3 | 6.8 | 11.3 | ||
Child (6–12 years) | 1.2 | 13.5 | 45.3 | ||
Adult (19–75 years) | 1.2 | 13.3 | 71.8 | ||
Adapted from [ | |||||
Pollutant | I hour (μg/m3) | 8 hours (μg/m3) | 24 hours (μg/m3) | Annual mean (μg/m3) | |
PM2.5 | 25 | 10 | |||
PM10 | 50 | 20 | |||
Adapted from | [ |
The absence of reference exposure levels for PM5.0, PM1.0, PM0.5, and PM0.3 means that relevant exposure thresholds do not yet have toxicological evidence of potential detrimental effects on human health.
Time spent by children and adults within the vicinity of the dumpsite.
CHILDREN | ADULT | |||||||
---|---|---|---|---|---|---|---|---|
Weekdays | Weekends | Weekdays | Weekend | |||||
Time (min) | % | Time (min) | % | Time (min) | % | Time (min) | % | |
NNR | 4 | 13.79 | 5 | 11.4 | 2 | 14.29 | 1 | 7.70 |
OAM | 3 | 10.35 | 2 | 4.54 | 2 | 14.29 | 1 | 7.70 |
UMR | 3 | 10.35 | 3 | 6.82 | 3 | 21.43 | 2 | 15.38 |
EER | 7 | 24.13 | 10 | 22.72 | 1 | 7.14 | 3 | 23.08 |
TER | 4 | 13.79 | 11 | 25.00 | 1 | 7.14 | 2 | 15.38 |
OOR | 5 | 17.24 | 6 | 13.63 | 3 | 21.42 | 2 | 15.38 |
AER | 3 | 10.35 | 7 | 15.91 | 2 | 14.29 | 2 | 15.38 |
Time spent by children and adults at the dumpsite.
S/N | Location | Wind speed | Wind chill | Temperature | Relative humidity | Humid index | Dew point | Wind direction |
---|---|---|---|---|---|---|---|---|
NNR | 2.4 | 28.5 | 29 | 81.3 | 37.7 | 27.6 | 250.20 SW | |
OAM | 4.3 | 29.5 | 28.7 | 71.5 | 36.9 | 26.6 | 118.00 NW | |
UMR | 2.5 | 28.5 | 28.5 | 79.9 | 31.6 | 26.7 | 237.00 NW | |
EER | 3.6 | 28.5 | 29 | 81.6 | 37.7 | 27.6 | 125.00 NS | |
TER | 4.3 | 29.5 | 28.7 | 81.5 | 36.9 | 26.6 | 245.00NW | |
OOR | 2.5 | 28.5 | 28.5 | 84.9 | 31.6 | 26.7 | 250.20 SW | |
AER | 2.5 | 28.5 | 28.5 | 82.9 | 31.6 | 26.7 | 118.00 NW |