Volatile Organic Compounds (VOCs)
Emitted from the Point of Combustion of
Charcoals Produced from Three Potentially Toxic Tree Plants in Nigeria
J S Gushit1*, H L Njila1, J M Daben1, M S Ayuba1, C Domchak2 and A I Abutu1
1Department of Science Laboratory Technology, University of Jos, Nigeria
2Office of Research and Development (ORD), University of Jos, Nigeria
Submission: March 15, 2021;Published: April 08, 2021
*Corresponding author: J S Gushit, Department of Science Laboratory Technology, University of Jos, Nigeria
How to cite this article: J S Gushit, H L Njila, J M Daben, M S Ayuba, C Domchak, et al. Volatile Organic Compounds (VOCs) Emitted from the Point of Combustion of Charcoals Produced from Three Potentially Toxic Tree Plants in Nigeria. Int J Environ Sci Nat Res. 2021; 27(5): 556222. DOI: 10.19080/IJESNR.2021.27.556222
In other to have empirical insight into the toxicity linked to indoor exposure to charcoal products used for commercial and domestic heating in indigenous Nigerian communities, three potentially toxic tree plants widely used for making charcoals, which includes ‘Gwaska’ (Erythrophleum sauveolens), ‘Kwalbiya’ (Prosopis spp) and ‘Tukpoku’ (African tulip: Spathodea campanulata), were identified from their natural habitats. They were processed into charcoals using indigenous kiln by the experts under the supervision of the research team. The processed charcoals were subjected to control combustion in a 21cm x 21cm x 15cm furnace from where the VOCs and other essential air quality parameters were detected from the venting outlet (chimney) with diameter 6.6cm, using calibrated indoor air detector (Air Master). The air quality parameters detected were VOCs, formaldehyde (HCHO), PM2.5, PM10, and % relative humidity (RH). Various VOCs were detected after characterizing the hot smoke emitted from each of the charcoal samples using Gas Chromatography Mass Spectrometry (GC-MS). Some of the VOCs such as toluene and carbonyl derivatives were potentially toxic, due to this, the work recommends that charcoals should not be produced from any of these tree plants under the conditions adopted in this research.
Use of charcoal and wood products have become almost unavoidable as it is the widely used source of energy for heating purposes in most developing nations. Because of the varieties of the sources of the charcoal products from different tree plants, some toxic chemical substances are often emitted during the burning processes. Among such substances are the volatile organic compounds (VOCs), full of uncertainties as the fate of these class of compounds cannot be clearly defined. Apart from being directly injurious to human and other living beings, they also affect the environment. For instance, VOCs containing halogens are potential green house and ozone depleting substances . They are widely released from burning fuel such as, gasoline, wood, coal, or natural gas. They are also emitted from oil and gas field and diesel exhaust. Their sources can also be traced to releases from solvents, paints, glues, and other products that are used and stored at home and at work place. The effect of these substances when inhaled ranges from dry mucous membrane and skin; irritation of eyes nose and throat, chest tightness, headache; and mental fatigue . Common examples of volatile organic compounds are gasoline, benzene, formaldehyde, carboxylic acid derivatives, solvents such as toluene and xylene, styrene and perchloroethylene (tetrachloroethylene)-the main solvent used in dry cleaning . Charcoal is a widely used household energy source used as the most predominant source of energy for heating in most households in developing nations and is fast becoming the source of most unintended VOCs in the environment. This study on VOCs is very important because apart from the health implication due to direct exposure to them, they also play strategic roles on atmospheric chemistry as they affect the formation of photochemical smog which dwindle the air quality and further threatens human health and the ecosystem . An earlier study has indicated that VOCs enters the bloodstream through inhalation, ingestion and the skin . This work detects and characterise the VOCs in potentially toxic tree plants being used in some places in Nigeria for making charcoals.
The study was carried out in Jos North and Bassa LGA
Metropolis of Plateau State (Figure 1), North Central Nigeria.
Jos North is located in the North-West part of the State, which
is situated on latitude 7° and 11°N and longitude 7° and 25° E
and at an average altitude of about 1200m above sea level; with
a population of about 873,943 at the Census, 2006 (although
quite a lot more now). Jos North and Bassa are Local Government
Areas in the northern part of Plateau State, Nigeria, bordering
Kaduna and Bauchi States. The topography of the area is
undulating grassland with scattered trees.
The samples used for this research were collected at Jengre,
Bassa LGA and Mazah, Jos North LGA, Plateau state, Nigeria.
Various grades of the charcoal were collected in polythene bag,
after which they were transported to the research area at the
Chemical Sciences Laboratories of University of Jos, Nigeria.
A combustion chamber made up of 21cm x 21cm x 15cm flat
sheet iron constructed furnace with a fume head (chimney) of
6.6cm diameter was used to carry out a controlled combustion of
the prepared charcoal samples. A calibrated indoor air detector
(Air Master) was used to detect the VOCs and other essential
quality parameters such as: HCHO, PM2.5, PM10, and % relative
humidity (RH) from the smoke emitted through the chimney.
Sampling device and collection of VOCs for characterization
The smoke fumes produced from a combustion chamber
were collected in a sampler which comprises glass sampling tube
(sorbet tubes) open at both ends and filled with activated charcoal
(Figure 2). Each opening in sampling tube is filled with cellulose
acetate diffusion barrier (cotton wool). The smoke fume diffuses
into the sampling tube in a controlled manner, keeping the cross
section, tube length diffusion coefficient constant.
After sampling, adsorption tubes were labeled and closed with
special caps to avoid contamination and desorption. The samples
were placed in tightly closed special plastic bags and kept in a
freezer until they were processed. Before analysis, contents of both
sections of the adsorption tubes were placed into two different
pre-weighed glass sample tubes, and 10ml dichloromethane
added as the desorption solvent to each tube. Samples were
extracted by shaking them in corked bottles using a magnetic
stirrer (Jenweary) for 30min. Ammonia was intermittently used
to elute the sample in the bottles. The extracted samples were
then purified in a micro chromatographic column filled with silica
gel (60-129 mesh) stored in a freezer until they were detected .
The VOCs compounds in the extracted solutions were
detected immediately after each desorption experiment using
gas chromatography coupled with mass spectrometric detection
(GC-MS). The model of the GC-MS used is Agilent GC 7890B, MSD
5977A, Agilent Technologies, USA. The GC column was eluded
with an initial oven temperature of 30°C increased to 60°C after
holding for 3min at a rate of 3°C min1 and finally to 240°C at the
rate of 45°C min-1. Helium was used as carrier gas at a constant
flow rate of 40ml min-1.
Table 1 provides the Local, English and Scientific names of the
three toxic tree plants used for the charcoal products indicated
with their corresponding samples codes (GWK, KWB and TPK).
Similarly, the VOCs, HCHO and Particulate Matters (PM2.5 & PM10)
detected from the smoke of the GWK, KWB and TPK are shown in
Table 2. The VOCs clearly indicated in Figure 2 is the total VOCs
and HCHO emitted which might be potential sources of the toxin
from the point of combustion of the charcoal samples. The highest
VOCs of 2.98mg/l was detected in the GWK Sample and TPK had
the least with 1.98mg/l recorded. These values are much higher
than value of 430μg/l reported for VOCs detected in the very
busy Apapa Industrial layout acclaimed to be a highly polluted
site in a the densely polluted city of Lagos . This suggests
the quality of smoke emitted from these charcoals is obviously
not environmentally friendly. On the other hand, formaldehyde
(HCHO) detected was in the range 0.33-1.24mg/l widely reported
to cause burning sensation to sensitive body organs like; nose,
throat and eyes. In severe case causes respiratory problem and
allergies. It has also been reported to cause cancer of the nasal
cavity . Constant exposure to these chemical substances by
using these charcoals for cooking and heating, leaves the users
under health threats as some of the VOCs (formaldehyde, toluene
etc) emitted are reported to be toxic, with other labelled as
potential carcinogens  (Figure 3).
On characterising the VOCs emitted from the samples
using GC-MS after sorption, desorption and purification,
the following compounds were detected; toluene, carbonyl
compounds (formaldehydes, 9-octadecenoic acid etc), silane,
3,4-methylenedioxymethamphetamine (MDMA) methylene
homolog, octadiene and phenol (Figures 3, 4 & 5). Most of these are
VOCs of interest owning to toxicity linked to them [10,11]. Toluene
for instance, was detected in GWK and KWB with composition
of 2% and 1% respectively. In terms of dominants, 5-diazo-1,3-
cyclopentadiene was detected in TPK with composition of 100%
(Table 3). Although there is limited literature on the toxicity of this
compound, more work still needs to be done on it to establish its
toxicity. It is however reported to be in the family of compounds
formed during pyrolysis . This was followed by total carbonyl
compounds detected from TPK smoke with composition of 93%
and a little with composition of 2% detected from KWB. Some
of the detected substances are; 9-octadecenoic acid, methyl
ester dodecanoic acid, 9,11-methyl ester-(E,E)-octadecadienoic
acid, heptadecanoic acid, 9,12-octadecadienal, cyclopentane
undecanoic acid, methyl stearate (Table 3). The compounds
eluted within the retention times range of 30 to 50min, at this
point the temperature is quite high in the oven (Figure 6). Since
these compounds were stable at relatively high temperature,
inhaling the hot smoke will expose end-users to toxic compounds.
Most VOCs are widely known for toxicity of varying degrees ,
as they take part in photochemical reactions that yield harmful
or even toxic products . For instance, the strategic signs and
symptoms associated with exposure to VOCs include conjunctival
irritation, nose and throat discomfort, headache, allergic skin
reaction, dyspnea, decline in serum cholinesterase levels, nausea,
emesis, epistaxis, fatigue and dizziness . These form the bulk
of complaints received on interacting with communities that are
using charcoal samples from these tree plants. It may not be too
far to affirm the report that VOCs cause serious health problems
as a number of them exhibit toxic, carcinogenic, mutagenic or
neurotoxic properties .
The occurrence of MDMA in GWK reported as a psychoactive
drug widely banned in most countries [17,18] with composition
of 92% is has answered the research question on the toxicity
of this charcoal as many of the end users end up complaining
of one health setback or other on long time exposure. With this
revelation, it is best not to use the plant (Gwaskaa) for charcoal
production. If there is no option, it must be remediated from this
compound before it is used.
Various VOCs were detected in the charcoal samples and some
of them are potentially toxic. Owing to the toxicity of the detected
VOCs from these plants, this work recommends that there should
be careful examination of any charcoal material used, because
of the likelihood of exposure to compounds that are injurious to
The Nigerian Government Tertiary Education Trust Fund
(TETFund) is acknowledged for supporting this research
financially. The authors would like to thank the Management
and Staff of University of Jos, Nigeria for allowing free access to
Laboratory facilities needed for this work.
Agency for Toxic Substances and Disease Registry –ATSDR (2001) Interaction profile of Benzene, Ethylbenzene, Toluene and Xylenes (BTEX) (draft for public comments) Atlanta, Agency for toxic Substances and diseases Registry, U. S Dept. of health and human services.
Chekwube OC, Majebi OJ, Sanni LM(2012) Baseline Level of Volatile Organic Compounds (VOCs) Pollution in Apapa Industrial Area of Lagos State, Southwestern Nigeria. Achives of Applied Sciences Research 4(6): 2564-2571.