The PM10 contributed in the e-waste dismantling community at Banmaichaiyaphot District, Buriram Province, was investigated due to the e-waste dismantling houses randomly located neighboring non-e-waste dismantling houses. The sampling was performed at non- and e-wastes dismantling houses and compared with the reference house in Daengyai subdistrict. The 24-hour average outdoor PM10 concentrations (81.957 ± 18.724 µg/m3) at e-waste dismantling sites were higher than those of the non-e-waste dismantling houses (80.943 ± 32.740 µg/m3) and control house (36.717 ± 19.516 µg/m3). The 24-hour average indoors PM10 concentrations of the e-waste dismantling houses (116.171 ± 64.635 µg/m3) showed higher concentrations than those of the non-e-waste dismantling (113.637 ± 64.641 µg/m3) and reference house (70.907 ± 22.464 µg/m3), but there were no statistically significant differences (P > .05). Both indoor and outdoor PM10 concentrations between non- and e-waste dismantling houses did not have significant differences, whereas those of non- and e-waste dismantling houses were significantly higher than that of the reference house locating approximately 5 km away. The positive correlation between indoor and outdoor concentrations of non- and e-waste dismantling houses was satisfactory significant with the r of .613 and .825, respectively. The results indicate that the existing indoor PM10 of either non- or e-waste dismantling houses could result from neighborhood e-waste dismantling.
At present, electronic and electrical appliances are a part of our daily lives such as mobile phones, televisions, refrigerators, washing machines, and computers. When these electronics are discarded, being nonworking, and having reached the end of their useful life, they will become electronic scraps called “Electronic waste or E-waste.”1 Because of the increase in consumption of electronics, e-waste has become one of the emerging problems in developed and developing countries worldwide. In Thailand, due to the increase of electronic and electrical appliance consumption, improper handling of electrical or electronic products and no regulation to manage e-waste directly, the problem of electronic waste is increasing every year. The estimated number of electrical and electronic equipment in Thailand increased from 359 070 to 414 600 tons in 2012 to 2017.2,3
The northeast of Thailand is one of the largest e-waste improper dismantling areas. For example, in Daengyai subdistrict, Banmaichaiyaphot District, and Banpao subdistrict, Puthaisong District, Buriram Province, there were 130 e-waste dismantling houses in 2017. The estimated number of e-waste entry to this area in 2017, including a desktop computer, fan, refrigerator, washing machine, television (CRT), were 1.88, 5.37, 8.26, 10.06, and 12.33 tons/y/household, respectively.4 The dismantling of these e-wastes is proceeded by informal separators or in the household in which primitive recycling techniques, such as cutting, breaking, smashing, and open burning, are used to separate the valuable parts for sale. After sorting, valuable materials such as copper, steel, aluminum, and plastic are sold, whereas the residue wastes such as debris, chips, foam, and other materials are disposed of in the dump site in the area. Inappropriate dismantling, as stated, will release the particulate matter (PM) into the air surrounding the dismantling area and also disperse into any indoor environment. Consequently, initiated air pollution can contribute to various respiratory problems.5 The dismantling workers may be posed to have potential health risks due to the PM contained in the hazardous materials passing through the alveolus of the workers or residents and reaching parts of the body through the blood circulatory system.6-8 Anyhow, most local people who have this occupation are not aware or are ignorant of the potential adverse health effects from dismantling of e-waste.
Contaminated outdoor air or PM could reach the indoor environment via penetration and ventilation. Opened windows and doors, as well as cracks in walls, doors, and window sealants, are the most common pathway which allows outdoor air to affect indoor air quality.9,10 Although outdoor air could affect indoor air quality, indoor sources could also affect the air quality itself. Occupants’ activities and the intended use of spaces were related to indoor pollutant sources. The most significant sources of indoor air pollution are gases and dust from cooking, in particular from using a stove with coal and tobacco smoke, followed by heating systems, cleaning, resuspension due to the presence of humans, and some were contaminated from the outdoor air. Then, outdoor air or dust of e-waste dismantling houses could penetrate through opened windows and doors which must contribute to indoor concentrations of dust even higher than outdoors.11,12 Moreover, the study of indoor/outdoor PM concentration or I/O ratio is an important indicator as the I/O ratio can portray the relationship between dust concentration indoors and outdoors, such as which one has more important sources or has more influence on the other’s levels.
When contaminated PM is released into the air, it can affect the air quality. The monitoring of PM usually uses respirable dust or PM that is less than 10 µm (PM10) because it is a useful indicator of the level, deposition, and distribution of contamination in the atmosphere derived from natural and anthropogenic activities and can be breathed in by people.13,14 Earlier studies have found the indoor PM10 concentration in the dismantling plant for the waste of electrical and electronic equipment cities.15 Another study detected PM10 around e-waste burning and industrial sites of Moradabad, India, where it was highest at industrial sites, and at e-waste burning site, it was higher than residential sites.13 There is some evidence that particulates could cause serious harm to humans via inhalation exposure, for example, bronchial irritation, inflammation, increased reactivity, reduced mucociliary clearance, reduced macrophage response.
Furthermore, the combustion from burning e-waste creates fine PMs, which is linked to pulmonary and cardiovascular disease.13,16 According to the above evidence of current e-waste dismantling houses widespread location in the communities in Northeastern Thailand, particularly in Daengyai, Banmaichaiyaphot District, Buriram Province, it is possible that PMs could disperse from e-waste dismantling houses to the air in the vicinity area. Consequently, the residents living in non-e-waste dismantling houses nearby might face contaminated air. Till now, the concentration and distribution of PM at non-e-waste dismantling houses in this area have not been studied. Thus, this study aims to investigate the concentration of PM10 in the residential area and to compare between those found in non- and e-waste dismantling houses.
Study area description
Daengyai subdistrict, Banmaichaiyaphot District, Buriram Province, in the northeast of Thailand was considered as a study area, and the location is shown in Figure 1. In the year 2017, there were 70 to 80 informal e-waste dismantling households approximately in this area. Six houses that have similar house floor plans (ie, 3 e-waste dismantling houses: A1-A3 and 3 non-e-waste dismantling houses: B1-B3) and 1 control house (approximately 5 km away from the e-waste dismantling region) were selected as the sampling sites for investigating the concentration of PM10, and there are 2 sampling points for each house, indoor and outdoor.
Sample preparation and collection
For filter preparation, a glass fiber filter was immersed in acetone for 10 to 15 minutes, then it was placed on a watch glass for drying and stored in a desiccator at 20 C to 30 C with a humidity of 30% to 40% for at least 2 days. The gravimetric method was used to determine the weight of pre- and postsampling filters by Mettler Toledo Ultra-Microbalance (7 digits) (UMX2) with 0.001 mg sensitivity. Prior to weighing a filter 3 times, standard pendulums of 100 and 200 mg were weighed for quality control. Next, the weighed filter was put into a filter cassette and sealed with parafilm, and then kept in a ziplock plastic bag for transferring to the sampling site.
The samples of PM smaller than 10 µm (PM10) were collected onto 37-mm glass fiber filters at 7 chosen sampling houses in both the dismantling and living area. Sampling points, indoors and outdoors, were set at approximately 1.0 to 1.5 m height from the ground. Before each sampling, a personal air pump connected with nylon cyclone and filter cassette was calibrated at a flow rate of 1.7 L/min, and the pump was measured again after sampling is finished. The sampling was taken 24 hours during the periods of December 22 to 28, 2017, consecutively.
After sampling, the filter cassette was sealed with parafilm and was placed in a ziplock bag for taking back to the laboratory and weighing the postsampling filter was done under the same conditions as before sampling. The total sample filters were 78 filters, 6 samples from the control house, and 36 samples each from the non- and e-waste dismantling houses. All indoor and outdoor samplings were conducted on the first floor of all sampling houses. For more additional data of the possible factor influences on PM10 contribution, house structure, and circumstance (closed or opened door and windows), and resident activities were also observed during the sampling. These additional data were then used to interpret the PM10 result.
Calculation of PM10 concentrations
Statistical analysis of the data was performed using the SPSS program (version 22). The analysis included (1) analysis of the mean difference in concentrations of PM10 between non- and e-waste dismantling houses and in indoor and outdoor concentrations using the t test method, (2) analysis of the different concentrations of PM10 in all sample houses by One-way analysis of variance, and (3) Pearson correlation was applied to investigate the correlation between indoor and outdoor PM10 concentrations.
Results and Discussions
Comparison of PM10 concentrations between indoor and outdoor air environment
The average 24-hour indoor PM10 concentrations at the selected 3 e-waste dismantling houses (A1, A2, and A3) were 130.703 ± 36.765, 130.318 ± 95.387, and 73.153 ± 13.444 µg/m3 as shown in Table 1, and those levels outdoors could be obtained at 91.619 ± 19.375, 80.074 ± 18.303, and 70.289 ± 13.914 µg/m3, respectively. The mean PM10 concentration of indoor 3 e-waste dismantling houses (116.171 ± 64.635 µg/m3) was higher than that measured outdoors (81.957 ± 18.724 µg/m3). This result reveals that PM10 concentration in the e-waste dismantling houses of this village was generally higher than the outdoors. However, the statistical analysis of mean differences between indoor and outdoor PM10 concentrations could not be found.
The 24-hour average PM10 concentration of non-, e-waste dismantling houses, and control house.
For 3 non-e-waste dismantling houses (B1, B2, and B3), the indoor PM10 concentrations were at the level of 123.483 ± 56.882, 88.127 ± 16.554, and 137.133 ± 113.190 µg/m3, respectively, which were higher than those outdoors, ie, 95.120 ± 36.640, 80.845 ± 35.478, and 59.827 ± 5.277 µg/m3, respectively. The mean PM10 concentrations of 3 non-e-waste dismantling houses from the indoor and outdoor areas were 113.637 ± 64.641 and 80.943 ± 32.740 µg/m3, respectively, which was similar to the result of the e-waste dismantling houses. Indoor and outdoor PM10 concentration was statistically analyzed, which showed that there were no statistically significant differences at 95% confidence level (Table 1).
At the control house, the mean of indoor PM10 concentrations was 70.907 ± 22.464 µg/m3, and it was 36.717 ± 19.516 µg/m3 for outdoor. This result shows that indoor PM10 concentrations were higher than outdoor. If comparing the mean concentration of 3 different houses with World Health Organization air quality guidelines (AQG) more than 24 hours (50 µg/m3), only the mean concentration of outdoor PM10 at the control house was lower than AQG.17
This study result shows a similar trend to the study on the relationship between indoor and outdoor concentrations of PM in rural residential houses in India which also found that the mean concentration of PM10 indoors (217.75 ± 66.62 µg/m3) was higher than outdoors (187.86 ± 41.01 µg/m3).18 Another study on indoor and outdoor dust around schools in Selangor, Malaysia, also found that the level of PM10 indoors (52.74 ± 16.90 µg/m3) mostly had higher concentration levels than outdoors (33.86 ± 17.41 µg/m3).19 Blondenau et al have emphasized that the larger the particles are in terms of optical diameter, the heavier they are and the more easily they can be deposited on floors and furnishings. Consequently, the influence of resuspension on indoor particle concentrations increases.20 Due to the environmental conditions at the indoors of the study was a mostly closed environment, there would be more dust precipitation than outdoors. And it is consistently influenced by resuspension, eg, house sweeping, wind pass through opened windows or doors, and household activities, especially cooking using a stove with coal. In addition, regarding the similar house characteristics of both non- and e-waste dismantling houses (mostly wooden houses) and location of the sampling houses was close to each other, all the same trends of indoor and outdoor PM10 concentration were observed.
Comparison of PM10 concentrations between non- and e-waste dismantling houses
The 24-hour average indoor PM10 concentrations of the non-, e-waste dismantling houses, and control house at indoor were 113.637 ± 64.641, 116.171 ± 64.635, and 70.907 ± 22.464 µg/m3, respectively, as shown in Table 1 and Figure 2, in which the levels at the e-waste dismantling houses were higher than those found at the non-e-waste dismantling houses and control house. However, there were no statistically significant differences at 95% confidence level between indoor PM10 concentrations of non-, e-waste dismantling houses, and the control house analyzed by ANOVA.
The average PM10 concentrations of the outdoor environment of the non-, e-waste dismantling houses, and control house were 80.943 ± 32.740, 81.957 ± 18.724, and 36.717 ± 19.516 µg/m3, respectively. Similar to the indoor environment, the outdoor PM10 of the e-waste dismantling house presented with a higher level than at the non-e-waste dismantling houses and control house. The statistical analysis of ANOVA was done to compare PM10 concentrations between non-, e-waste dismantling houses, and control house as summarized in Table 1. The result shows that the PM10 concentrations of non- and e-waste dismantling houses were not significantly different at 95% confidence level, whereas both were significantly higher than the control house. This analysis of no significant difference pointed out that the outdoor PM10 concentration in the vicinity of the e-waste dismantling community was not much different but still higher than that of non-e-waste dismantling area. When comparing the PM10 concentrations at the control house with concentrations at non- and e-waste dismantling houses, the result reveals that the concentrations at the control house were greatly lower than those measured at both sampling areas.
The higher PM10 at e-waste dismantling house could be generated from manually mechanical processes. The bulky e-waste taken for disassembly during the sampling was television, washing machine, refrigerator, desktop computer, and air conditioner. At the same time, other small appliances such as fan, rice cooker, printer, and electric jar pot were found in a lower proportion. These main types of e-wastes, in particular, the bulky e-waste gathered to this study site, were also reported by Thongkaow et al4 and Puangprasert and Prueksasit.21 The workers dismantled e-waste manually at their houses using primitive methods, ie, drilling, cutting and milling, and burning to separate, and recovered the saleable electrical components and precious materials. Such dismantling processes could then lead to elevate PM10 in their residential area and also distribute to the neighboring area. This evidence signified that the e-waste dismantling activities could contribute PM10 to the air and be considered the significant source of PM10 in this community.
There are previous studies on the PM10 around e-waste dismantling and burning areas and e-waste recycling industrial sites. For example, there was a study on appraisement of heavy metals in respirable dust (PM10) around e-waste burning and industrial sites of Moradabad, India, in which it had been found that the highest mean concentration of PM10 was at the industrial sites and e-waste burning site (200 ± 3.05 µg/m3) where it was significantly higher than the residential sites (126 ± 11.26 µg/m3).13 Furthermore, the study on PM10 distribution in a typical printed circuit boards manufacturing workshop also indicated that the concentrations of PM10 in the workshops ranged from 27.1 to 289.8 µg/m3, which was higher than the level observed in the off-site area (90.0 µg/m3).22 As mentioned above, primitive e-waste dismantling activities such as separating electronics equipment or appliances using a hammer, chisels, and screwdrivers or the recycling process in the industry can be considered the possible contribution source of PM10 in the air.
Relationship of indoor and outdoor PM10 concentrations in e-waste dismantling community
Pearson correlation analysis was performed to examine the relationship between indoor and outdoor PM10 concentrations in an e-waste dismantling community. As presented in Figure 3, indoor concentrations of non-e-waste dismantling houses were correlated with outdoor concentrations (r = .613) and the concentrations of e-waste dismantling houses had a good correlation between indoor and outdoor (r = .825). As mentioned above, house characteristics between e-waste or non-e-waste house are almost the same, which most houses are 1-story wooden, but some lesser part is half wood and concrete. Each house has its own open ground space with soil cover, where it is usually used for dismantling in the case of e-waste houses. Most houses have been built no less than 20 years and have a cross-natural ventilation system through opened doors and windows. This house configuration could enhance the PM10 blew into the inside area and might cause the significant correlations obtained from either e-waste or non-e-waste house mentioned above. The high PM10 presented inside the house that had e-waste dismantling could be increased from the high outdoor concentration even though the concentration indoors itself was usually high.
From the study on characterizing the indoor-outdoor relationship of fine PM in the non-heating season for urban residences in Beijing, there was a significant and strong positive correlation (r ⩾ .90) between indoor and ambient PM2.5 mass concentrations over the 24-hour sampling period as well as the 4 sessions, including at morning (6:00-12:00), afternoon (12:00-18:00), evening (18:00-0:00), and night (0:00-6:00). The results indicated that the indoor and ambient PM2.5 mass concentrations highly correlated with each other on a community basis. Even though excluding smoking families, there was still a strong correlation for all results of 4 sessions.23
Theoretically, indoor air particle concentrations can be influenced either by the infiltration of outdoor pollutants into the homes through opened windows and cracks or by particles from indoor sources. This may be significant for a house with poor sealing as due to these mechanisms, air pollutants from outdoors can penetrate into the indoor environment.6
I/O ratio of PM10 concentrations at non- and e-waste dismantling houses
From indoor and outdoor ratio, the result shows that PM10 concentrations in this area are usually higher indoors than outdoors as the average I/O ratio of non-, e-waste dismantling houses was higher than 1 (1.579 ± 1.153 and 1.367 ± 0.486, respectively), especially at the control house (2.086 ± 0.615). The mean I/O ratio of all sampling points in this study was higher than from the study on indoor air quality differences between urban and rural preschools in Korea with an I/O ratio of 1.35 in rural areas.24 The high PM10 concentrations indoors might be derived from other important indoor sources, including combustion, candles, and cooking. When considered at e-waste dismantling houses, the average I/O ratio was lower than the non- and control houses, which represents that the outdoor levels of PM10 of the e-waste dismantling houses were increased and had an effect on the indoor environment. Outdoor PM10 levels of dismantling houses increasing and making the I/O ratio decrease could indicate that dismantling activities have contributed to PM10 concentration in this area. Although Pearson correlation results showed the strong relationship between outdoor and indoor PM10 concentrations, they could suggest that there were usually high concentrations of indoor PM10 from other indoor sources of this area as shown from the I/O ratio in Table 2. The I/O ratio of PM10 more than 1 obtained from the previous studies in Table 3 suggests that the building envelope of houses and schools may not inhibit the resuspension or infiltration of particles indoor,24,26,27 whereas the I/O ratio lower than 1 indicates the absence of significant indoor sources.25 Furthermore, some factors may directly resulting in increasing or decreasing of I/O ratio such as differences in building envelope tightness, construction materials of houses, seasonal effects, building air exchange rates, and building design. Also, the human presence, occupancy rates and occupant activities such as walking and using chalk are the other significant factors controlling indoor/outdoor pollution ratios.26
Indoor and outdoor PM10 concentration ratio (I/O) of non-, e-waste dismantling houses, and control house.
Indoor and outdoor PM10 concentration ratio (I/O) of residential and school building.
The dismantling activities of e-waste processed by informal separators or in family-run workshops in this study could affect a noticeable contribution of PM10 concentrations in both indoor and outdoor environments. The PM10 concentration indoors being mostly higher than outdoors could be consistently influenced by resuspension and household activities. In addition, if non- and e-waste dismantling houses are located nearby each other in the same village, then existing indoor PM10 could result from the neighborhood e-waste dismantling house. The PM10 found at both non- and e-waste dismantling houses was significantly higher than at the control house, which indicates that e-waste activities could be a point source of PM10 emitted to the air. The strong correlation between outdoor and indoor PM10 levels at non- and e-waste dismantling houses is a sign of e-waste dismantling activities not only affecting the contribution of PM10 outdoors but also affecting indoors as well. Similar house floor plans and characteristics in this area are considerable to cause a better spread of PM10 between the outside and inside. However, the I/O ratio was found to be more than 1 at all sampling houses and revealed that the level of PM10 in the indoor environment was regularly higher in the study area. But the e-waste dismantling activities support the increase of PM10 concentrations in both the indoor and outdoor areas. From this overall study, e-waste dismantling activity was the main influence for increased PM10 concentrations in a residential area. Further studies on PM10 and other significant contaminants in PM10 as spatial and temporal distribution are required to elucidate the real effect of family-run e-waste dismantling houses.
Our thanks go to Dr Narut Sahanavin, Department of Public Health, Faculty of Physical Education, Srinakharinwirot University, for supporting air sampling equipment. We would also appreciate Interdisciplinary Program in Environmental Science, Graduate School, Chulalongkorn University for laboratory space and facilities. Moreover, we do deeply grateful to all local organizations and houses owner for their cooperation with the researchers and the involved authorities.
All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by SC and YK. SC wrote the first draft of the manuscript, and TP commented and corrected the manuscript finally. All authors read and approved the final manuscript.