The results revealed the rationale behind this study which is to ascertain the pollution level of e-waste activities (burning of e-waste at treatment points) posed to the extractors and the people around the treatment points. It reveals the concentration of heavy metals (Cd, Cu, and Pb) there in, the concentration in relation to set threshold and the assessment of human health risks (carcinogenic and non-carcinogenic) people are exposed to.
The e-waste burning engaged by the extractors is solely for economic gain as valuable resources are extracted from the burnt materials which cater for the livelihoods of the extractors and their family. The government also gains from this activity by collecting tax and revenue from the extractors and agents that are engaged in e-waste activities. Notwithstanding, their activities pollute the environment and posed a threat to the well being of the extractors and the public residing around the treatment points. This is a thing of concern and has prompt for undertaking this study in order to safeguard the environment and the populace.
Heavy Metal Concentration at E-Waste Burning Sites
The heavy metal concentrations were revealed and risk assessments for non-carcinogenic and carcinogenic ailments were analyzed.
Table 4: Heavy metal concentration at E-waste treatment points (Burning)
Locations of Treatment point (Burning)
|
Cd Conc. (ppm)
|
Cu Conc. (ppm)
|
Pb Conc. (ppm)
|
Kuka Bulukiya
|
|
|
|
(0m) Sample 1
|
0.0025
|
0.0513
|
0.0775
|
(5m) Sample 2
|
0.0052
|
0.0512
|
0.0652
|
(10m) Sample 3
|
0.0051
|
0.0550
|
0.0651
|
Mean Conc.
|
0.0042
|
0.0525
|
0.0693
|
(100m) Control
|
0.0015
|
0.0037
|
0.0052
|
PRP Gidan Ruwa
|
|
|
|
(0m) Sample 1
|
0.0075
|
0.0352
|
0.0070
|
(5m) Sample 2
|
0.0053
|
0.0412
|
0.0675
|
(10m) Sample 3
|
0.0051
|
0.0325
|
0.0725
|
Mean Conc.
|
0.0059
|
0.0363
|
0.049
|
(100m) Control
|
ND
|
0.0027
|
0.0097
|
ND = Not Detected
The heavy metal concentration (Cd, Cu, and Pb) is shown in Table 4 in the various samples analyzed at the two treatment points (Kuka Bulukiya and PRP G/Ruwa). The results of the analysis at Kuka Bulukiya treatment point revealed Pb has the highest mean concentration of 0.0693 ppm, followed by Cu 0.0525 ppm and Cd having 0.0042 ppm. However, the control concentration of heavy metal was relatively lower than the concentration of the samples at the treatment points. Cd was found to be 0.0015 ppm, Cu was 0.0037 ppm, and Pb was 0.0052 ppm respectively, this might not be unconnected with pollution from other sources within the urban environment. This implies that there are heavy metal pollution activities taking place at the treatment points, which is a thing of concern for the extractors, public and environmental health. The concentrations at PRP G/Ruwa was found to be similar to the one at Kuka Bulukiya but the mean concentration of Cd which was found to be 0.0059 ppm is slightly (significant) more than the concentration at Kuka Bulukiya. However, the mean concentration of Cu which was 0.0363 ppm and Pb which was 0.049 ppm is slightly lower than the concentrations at Kuka Bulukiya as seen in Table 4. The Cu concentration for control at PRP G/ruwa was found to be 0.0027 ppm which was slightly lower and for Pb it was 0.0097 ppm which was higher than the control concentration at Kuka Bulukiya respectively. However, Cd concentration at PRP G/Ruwa was not detected (ND), this implies that the concentration might be negligible and below the detection limit of the equipment. The result of the analysis (Table 4) in the two treatment points (K/Bulukiya and PRP G/Ruwa) is higher than the concentrations of Cu 2.468 µg/m3 (0.00247 ppm) and Cd 0.008 µg/m3 (0.000008 ppm) in the study of Kim et al. (2010) on the characteristics of atmospheric heavy metals in subway station in Seoul. This implies the contributions of e-waste burning materials in the results of the analysis obtained. However, the study of Adaramodu et al. (2012) on the concentration of metals of surface dust in e-waste components of the Westminister electronic market, Lagos for Pb (outdoor dust) 15.90 mg/kg and Cd (outdoor dust) 1.80 mg/kg is way higher than the result in this analysis (Table 4). Other similar studies on exposure to the heavy metals of e-waste workshops and recycling point are (Xu et al. 2015) and (Wu et al. 2016).
Heavy metal concentration in relation to set threshold and its implications
However, the result of the analysis in relation to NESREA standards for point source maximum emission limit for facilities and process, and for ambient air quality standards is shown in Table 5. The analysis discovered that the concentration of Cd, Cu, and Pb at the two treatment points (Kuka Bulukiya and PRP G/Ruwa) is lower than the NESREA (2014) set threshold for point source maximum emission limit for facilities and process from any source (Table 5). More so, the ambient air quality standards set by NESREA (2013) for concentration of Cd (0.38 ppm) and Pb (3759 ppm) is higher than the concentration of Pb (0.063 ppm) and (0.049 ppm), and Cd (0.0042 ppm) and (0.0059 ppm) at both Kuka Bulukiya and PRP G/Ruwa treatment points respectively. The USEPA (2016b) National Ambient Air Quality Standards (NAAQS) for lead stipulated the primary and secondary standards to be 0.15µg/m3 for 3 months average which is lower than the concentration obtained in this study for the two treatment points. European Commission (2000) assigned a 0.2 to 2.5 ng/m3 for ambient air pollution by cadmium at urban background which is lesser than the mean concentration for the two treatment points in this study.
Of importance is the consideration for the extractors/collectors, public and environmental health that need to be checked (Plate 1). There is tendency of accumulation of these heavy metals over time which might result to myriad of health and environmental problems. Of concern is that there are lots of buildings (houses and schools) surrounding the treatment points at K/Bulukiya, a football field where football is played by both children and adults, children that comes to the pond to catch fish and swim, that inhale the burnt e-waste are at risk or might potentially face several health challenges (Plate 1). There is Kuka Bulukiya primary school and GJSS (Plate 1) nearby that houses children (which are vulnerable) during school hours while these burning (e-waste) activities takes place.
Table 5: Heavy metals concentration in air at e-waste treatment points in relation to NESREA threshold
|
Treatment point
|
Treatment point
|
NESREA (2014) point source max. emission limit for facilities and process
|
|
NESREA (2013) ambient air quality standards
|
|
pollutants
|
Kuka Bulukliya conc. (ppm)
|
PRP G/Ruwa conc. (ppm)
|
Standard applicable to source
|
Maximum permissible limit (ppm)
|
Time weighted average
|
Maximum permissible limit (ppm)
|
Cadmium
|
0.0042
|
0.0059
|
Any source
|
2.0
|
annual
|
3759
|
Copper
|
0.0525
|
0.0363
|
Any industrial source
|
36
|
annual
|
-
|
Lead
|
0.0693
|
0.049
|
Any trade industry or process
|
1.1
|
annual
|
0.38
|
Source: Field survey (2020), NESREA (2014), NESREA (2013)
Of interest is that at PRP G/Ruwa treatment point during the burning of e-waste materials, air or smoke settles or moves over the nearby vegetable farmland which might lead to bioaccumulation of these metals (Cd, Cu, and Pb) on the farm produce with the potential of causing unforeseen danger to the consumers and nearby houses. Liu et al. (2021) indicated that the results of a study conducted on heavy metals in soil/vegetable system close to e-waste site in China showed that both adults and children were suffering from health risk. It further narrated that the consumption of lettuce and sweet potato caused the most health risk and also revealed that cowpea and cabbage were moderately safe. Another study by Yin et al. (2021) revealed that there is a reasonable pollution of PBDEs and heavy metals there in the vegetables in a regulated e-waste recycling site, Eastern China.
Another public health implication of burning of e-waste materials in open place is that the extractors/collectors and people living around the area do not use any form of protection (face and hand gloves) for safety during burning and this poses a health related menace to the extractors, environment and the public.
However, it is worth noting that children residing close to PRP G/Ruwa treatment point especially, come to the treatment point to sell sachet water and in the process inhaling and ingesting the contaminants there in the burning activities and another activity worth noting is that there are wood cutters just about 1.5 m to the treatment point which this open burning will be a threat to their well being.
The major implication of these heavy metals is that they are toxic at low levels of exposure. In addition, both acute and chronic exposure are a threat to humans and the environment, that is a single exposure to harmful substances and those that occurs over a long period of time and that its health effects are cumulative. Similarly, they tend to build up in crucial organs like kidney, brain, liver, and bones, for number of years leading to serious health problems once they are absorbed by the body (Kamunda et al. 2016). The effect of over time accumulation of inhaled cadmium is adverse kidney, bone and liver damage, and cancer and for lead is delays in neurological development, physical development and damage, and damage of renal function, hearing loss, anaemia, and blood pressure (WHO 2007). Furthermore, Pb disturbs the functioning of kidneys, reproductive issue and the nervous system, and also induces renal tumor. Severe exposure to Cd has its effect such as emphysema, alveolitis, and bronciolitis (Pendias 2011). Cd may also lead to kidney malfunction, hypertension, bone fracture, and cancer (Khan et al. 2013). Anaemia, cardiovascular diseases, reduced fertility, arthritis, cirrhosis, and strokes are seen as some of its effect in a long run (Kamunda et al. 2016). Excessive exposure to Cu may lead to noncarcinogenic effects on human health, meanwhile they are crucial to human life, its surplus has been linked with liver damage (Cao et al. 2010).
Health Risk Exposure Assessment
The health risk exposure assessment in this study comprises of both noncarcinogenic and carcinogenic assessment of the health risk in the burning of e-waste materials at K/Bulukiya and PRP G/Ruwa treatment points. Exposure of the extractors and the people living around the treatment points that likely inhaled, ingested, and had dermal contact with the contaminated air is considered in this assessment. This assessment predicts the possible non-cancerous and cancerous health risk exposed by adult and children at both treatment points by integrating data generated (Table 2 and 3) to arrive at the estimates of hazard indices and cancer risk through different pathways (inhalation, ingestion, and dermal contact) of identified heavy metals (Cd, Cu, and Pb) there in.
Noncarcinogenic Risk of Heavy Metals
Based on the RfD values (Table 3) and ADI values (Table 6), the noncarcinogenic risk for adults and children were calculated. The results for the pathways (inhalation, ingestion, and dermal) were all expressed in terms of hazard quotient (HQs) and its summation expressed in terms of hazard indices (HI) in Table 6. The HQs and HI gave the prediction of the potential noncarcinogenic health risk exposed by the populace.
The standard is that when HQ and HI values are not up to 1, it means there is no clear potential risk of noncarcinogenic effects to the population, though if these values surpass 1, there may be concerns (US EPA 2004). The result of the adult population calculated shows that the HQ (Figure 1, 2, 3 and 4) and HI values are less than 1 in all the pathways (inhalation, ingestion, and dermal) at both Kuka Bulukiya and PRP G/Ruwa treatment points (1.2 ˟ 10-4 and 9.8 ˟10-5) respectively (Table 6).
Figure 1 and 2 shows the hazard quotient for Kuka Bulukiya for adult and children for all the pathways (inhalation, ingestion and dermal) and for the contaminants under study (Cd, Pb and Cu). The standard for the values used in the conversion of the figures was 1˟ 10-6.
This meant that the populations are not at risk of noncarcinogenic effects. However, dermal and ingestion contributed more followed by inhalation in that order at both treatment points. In essence, the result for the children revealed that the HQ and HI are less than 1, for all the pathways at both treatment points at Kuka Bulukiya 6.4 ˟ 10-4 and PRP G/Ruwa 5.9 ˟10-4 (Table 6). This meant children populations are not at risk of noncarcinogenic health effects based on the calculation of health risk assessment due to the concentration of the heavy metals in this study.
Figure 3 and 4 shows the hazard quotient for PRP G/Ruwa for adult and children for all the pathways (inhalation, ingestion and dermal) and for the contaminants under study (Cd, Pb and Cu). The standard for the values used in the conversion of the figures was 1˟ 10-6.
3.3.2 Cancer Risk Assessment of Heavy Metals
Based on the carcinogenic risk assessment values calculated, the lifetime average daily dose (LADD) values in Table 7 and cancer slope factor (CSF) in Table 2 revealed the health risk threat faced by the extractors and the public. The lifetime risk assessment for adults and children contributed by different heavy metals for all the pathways in Table 7 is shown.
The carcinogenic risk was calculated for Cd, Cu, and Pb where Pb was found to be the major contributor in this assessment (Figure 5, 6, 7 and 8). The US EPA (2004) considers 1 ˟ 10-6 to 1 ˟ 10-4 to be the range of the standard for cancer risk purposes. The cancer risk for Kuka Bulukiya 6 ˟ 10-10 and PRP G/Ruwa 5 ˟ 10-10 for adults and 7 ˟ 10-10 and 4 ˟ 10-10 for children (Table 7) were both lower than the threshold set for cancer risk. Figure 5 and 6 shows the cancer risk potential for Kuka Bulukiya for adult and children for all the pathways (inhalation, ingestion and dermal) and for the contaminants under study (Cd, Pb and Cu). The standard for the values used in the conversion of the figures was 1˟ 10-9.
This meant that both adults and children are not at risk of cancer based on the assessment in this study at the treatment points. The ingestion contributed more to cancer risk assessment then followed by inhalation pathway. However, due to the non-availability of cancer slope factor (CSF) for the dermal pathway it was not part of the assessment. Though, there is need for caution since there is hazard identification at the treatment points and authorities should act accordingly.
Figure 7 and 8 shows the cancer risk for PRP G/Ruwa for adult and children for all the pathways (inhalation, ingestion and dermal) and for the contaminants under study (Cd, Pb and Cu). The standard for the values used in the conversion of the figures was 1˟ 10-9.
Lead toxicity is apparent as it contributes more in the results revealed followed by cadmium, and copper contributed the least in the calculation at both Kuka Bulukiya and PRP G/Ruwa treatment points
Table 6: Average Daily Intake (ADI) Values in mg/kg.day, Hazard Quotient (HQ) and Hazard Index (HI) for Adults and Children at the E-waste Burning Sites for Noncarcinogenic Risk Calculations
Heavy metals
|
ADIinh Adult
|
ADIing Adult
|
ADIderm Adult
|
ADIinh
Children
|
ADIing
Children
|
ADIderm
Children
|
HQinh Adult
|
HQing Adult
|
HQderm Adult
|
HQinh Children
|
HQing Children
|
HQderm Children
|
HI Adult
|
HI Children
|
K/Bulukiya
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cd
|
4.74 ˟ 10-12
|
5.8 ˟ 10-9
|
2.3 ˟ 10-9
|
1.42 ˟ 10-11
|
4.6 ˟ 10-8
|
9.7 ˟ 10-9
|
1.9 ˟ 10-6
|
1.2 ˟ 10-5
|
4.6 ˟ 10-6
|
5.9 ˟ 10-6
|
9.2 ˟ 10-5
|
1.9 ˟ 10-5
|
1.9 ˟ 10-5
|
1.2 ˟ 10-4
|
Cu
|
5.93 ˟ 10-11
|
7.2 ˟ 10-9
|
2.9 ˟ 10-8
|
1.78 ˟ 10-10
|
5.8 ˟ 10-7
|
1.2 ˟ 10-7
|
1.5 ˟ 10-9
|
1.9 ˟ 10-7
|
1.2 ˟ 10-6
|
2 ˟ 10-10
|
1.6 ˟ 10-6
|
5.0 ˟ 10-6
|
1.4 ˟ 10-6
|
6.6 ˟ 10-6
|
Pb
|
7.92 ˟ 10-11
|
9.5 ˟ 10-8
|
3.85 ˟ 10-8
|
2.35 ˟ 10-10
|
7.6 ˟ 10-7
|
1.6˟ 10-7
|
2.3 ˟ 10-8
|
2.6 ˟ 10-5
|
7.3 ˟ 10-5
|
6.7 ˟ 10-8
|
2.1 ˟ 10-4
|
3.0 ˟ 10-4
|
9.9 ˟ 10-4
|
5.1 ˟ 10-4
|
Total
|
-
|
-
|
-
|
-
|
-
|
-
|
1.9 ˟ 10-6
|
3.8 ˟ 10-5
|
7.8 ˟ 10-5
|
5.9 ˟10-6
|
3.0 ˟ 10-4
|
6. 3 ˟10-4
|
1.2 ˟ 10-4
|
6.4 ˟ 10-4
|
PRP G/Ruwa
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cd
|
6.67 ˟ 10-12
|
8.1 ˟ 10-9
|
3.28 ˟ 10-9
|
1.99 ˟ 10-11
|
6.8 ˟ 10-8
|
1.4 ˟ 10-8
|
2.8 ˟10-6
|
1.6 ˟10-5
|
6.6 ˟10-6
|
8.3 ˟10-6
|
1.4 ˟10-4
|
2.7 ˟10-5
|
2.5 ˟10-5
|
1.8 ˟10-4
|
Cu
|
4.1 ˟ 10-11
|
4.97 ˟ 10-8
|
2.02 ˟ 10-8
|
1.23 ˟ 10-10
|
3.9 ˟ 10-7
|
8.4 ˟ 10-8
|
1.0 ˟10-9
|
1.3 ˟10-6
|
8.4 ˟10-7
|
3.0 ˟10-8
|
1.0 ˟10-5
|
3.5˟ 10-6
|
2.1 ˟10-6
|
1.4 ˟10-5
|
Pb
|
5.53 ˟ 10-11
|
6.71˟ 10-8
|
2.73 ˟ 10-8
|
1.66 ˟ 10-10
|
5.4 ˟ 10-7
|
1.3 ˟ 10-7
|
1.6 ˟10-8
|
1.9 ˟10-5
|
5.2 ˟10-5
|
4.7 ˟10-8
|
1.5 ˟10-4
|
2.5 ˟10-4
|
7.1 ˟10-5
|
4.0 ˟10-4
|
Total
|
-
|
-
|
-
|
-
|
-
|
-
|
2.8 ˟10-6
|
3.6 ˟ 10-5
|
5.9 ˟10-5
|
8.4 ˟10-6
|
3.0 ˟10-4
|
2.8 ˟10-4
|
9.8 ˟10-5
|
5.9 ˟10-4
|
Table 7: Lifetime Average Daily Dose (LADD) in mg/kg.day and Hazard Cancer Risk for Adult and Children at E-waste Material Burning Sites for Carcinogenic Calculations
Heavy metals
|
LADDinh Adult
|
LADDing Adult
|
LADDderm Adult
|
LADDinh Children
|
LADDing Children
|
LADDderm Children
|
Cancer Riskinh Adullt
|
Cancer Risking Adult
|
Cancer Riskderm Adult
|
Cancer Riskinh Children
|
Cancer Risking Children
|
Cancer Riskderm Children
|
Total Cancer Risk Adult
|
Total Cancer Risk Children
|
K/Bulukiya
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cd
|
1.7 ˟ 10-11
|
2.1 ˟ 10-9
|
8 ˟ 10-10
|
1.0 ˟ 10-12
|
3.3 ˟ 10-9
|
6.0˟ 10-8
|
1.0 ˟ 10-10
|
-
|
-
|
6.4 ˟ 10-11
|
-
|
-
|
1 ˟ 10-10
|
6.4 ˟ 10-11
|
Cu
|
2.1 ˟ 10-10
|
2.6˟ 10-8
|
1.1 ˟ 10-8
|
1.3 ˟ 10-11
|
4.1˟ 10-8
|
8.6 ˟ 10-9
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Pb
|
3.0 ˟ 10-10
|
5.2 ˟ 10-8
|
1.4 ˟ 10-8
|
1.7 ˟ 10-11
|
5.4 ˟ 10-8
|
1.4 ˟ 10-8
|
1.3 ˟ 10-10
|
4 ˟ 10-10
|
-
|
7.0 ˟ 10-11
|
5 ˟ 10-10
|
-
|
5 ˟ 10-10
|
1.2 ˟ 10-10
|
Total
|
-
|
-
|
-
|
-
|
-
|
-
|
2 ˟ 10-10
|
4 ˟ 10-10
|
-
|
1.5 ˟ 10-10
|
5 ˟ 10-10
|
-
|
6 ˟ 10-10
|
7 ˟ 10-10
|
PRP G/Ruwa
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cd
|
2.4˟ 10-11
|
2.9 ˟ 10-9
|
1.2 ˟ 10-9
|
1.4 ˟ 10-11
|
4.6 ˟ 10-9
|
1.0 ˟ 10-9
|
1.0 ˟ 10-10
|
-
|
-
|
8.9 ˟ 10-11
|
-
|
-
|
1 ˟ 10-10
|
8.9 ˟ 10-11
|
Cu
|
1.5 ˟ 10-10
|
1.8 ˟ 10-8
|
7.2 ˟ 10-9
|
8.7 ˟ 10-11
|
2.8 ˟ 10-8
|
6.0 ˟ 10-9
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
Pb
|
1.9 ˟ 10-10
|
2.4 ˟ 10-8
|
9.7 ˟ 10-9
|
1.2 ˟ 10-10
|
3.8 ˟ 10-8
|
8.1 ˟ 10-9
|
2.0 ˟ 10-10
|
2 ˟ 10-10
|
-
|
4.9 ˟ 10-11
|
3 ˟ 10-10
|
-
|
4 ˟ 10-10
|
3 ˟ 10-10
|
Total
|
-
|
-
|
-
|
-
|
-
|
-
|
3 ˟ 10-10
|
2˟ 10-10
|
-
|
1.3 ˟ 10-11
|
3 ˟ 10-10
|
-
|
5 ˟ 10-10
|
4 ˟ 10-10
|
Climate Change Adaptation
This study has highlighted the threat posed by burning of e-waste materials and this contributes to climate change due to the chemicals released. This implies that the released chemicals (heavy metals, polybrominated biphenyls and toxins) accumulate in the air and posed severe health implications to the environment, humans and animals. E-waste being a contemporary area of study has limited studies on its activities adaptation to climate change. Climate change adaptation has to do with an environmentally friendly method of extracting valuable materials that should be at the forefront of policies that will be specifically enacted on e-waste management in developing countries. Taking back system and encouraging environmentally sound recycling and refurbishing alternatives will help in climate adaptation. Regulations should be in place to promote sustainable e-waste dismantling, extraction (by discouraging or stopping open burning of e-waste) facility and on how to capture the contaminants released into the air. Tree planting should be encouraged and a formal e-waste treatment points should be identified and allow only environmentally friendly activities to take place, and a penalty should be set aside for policy and regulation averters.