Chemical contaminant exposures assessed using silicone wristbands among fuel station attendants, taxi drivers and commercial motorcycle riders in Kampala, Uganda

Abstract

There are concerns over traffic-related air pollution in Uganda’s capital, Kampala. Individuals in the transportation sector are hypothesized to be at greater risk for exposure to volatile organic compounds, given their proximity to vehicle exhaust. Silicone wristbands are a wearable technology that passively sample individuals’ chemical exposures. We conducted a pilot cross sectional study to measure personal exposures to volatile organic compounds among 14 transportation workers who wore a wristband for five days. We analyzed for 75 volatile organic compounds; 33 chemicals (35%) were detected and quantified in at least 50% of the samples and 15 (16%) chemicals were detected and quantified across all the samples. Specific chemicals were associated with participants’ occupation. The findings can guide future large studies to inform policy and practice to reduce exposure to chemicals in the environment in Kampala.

Keywords:

• Chemical contaminant
• commercial motorcycle riders
• exposure assessment
• fuel station attendants
• silicone wristband
• taxi drivers
• Uganda

Introduction

Air pollution concerns are increasing globally, mostly affecting populations in low-income countries where air quality in nearly all (97%) cities fall below the World Health Organization recommendations.¹ In urban areas, traffic-related pollution, comprising primarily exhaust emissions from motor vehicles, road abrasion and tyre and brake wear, is of particular concern.^1,2 Similarly, volatile organic compounds (VOCs) and other petrochemical organic emissions are increasing environmental chemicals to which people are exposed.³ An increase in ambient air pollution levels in Uganda has been observed which highlights a need to generate more evidence on air pollution exposures in the country.⁴ In Kampala city and other urban centers in the country, growing chemical exposures are anticipated due to rapidly increasing vehicle usage, increased traffic congestion, adulterated fuel, and insufficient technical standards for inspection and maintenance of vehicles.^5,6 A study in Uganda found that the air quality in the city center, particularly at public transport holding stations was hazardous for inhalation.⁷ Exhaust fumes and oil spills are also common sources of hazardous exposures among fuel pump attendants.^8,9 Individuals are constantly exposed to mixtures of chemicals which have differing toxicities.^10,11 Annually, environment related factors are linked to approximately 24% (13.7 million) of global deaths.¹² People are exposed to a wide range of environmental and occupational pollutants including chemicals associated with an increased risk of diseases including cancers of the lung, skin, urinary bladder, and breast.^13–20 Such cancers are increasing in low-income countries including Uganda.^21,22

Volatile Organic Compounds (VOCs) and other petrochemical organic emissions are increasing chemicals to which people are exposed.³ These organic solvents and VOCs are used in many occupations in urban areas and have both direct and indirect health effects including eye and respiratory tract irritation, headaches, visual disorders, skin allergies and irritations, fatigue, and memory damage,^23–26 Specifically, flame retardants have been associated with cardiotoxicity, reduced hormone levels, and neurotoxicity.^27–30 Exposure to Naphthalene, a potential human carcinogen,³¹ is associated with hemolytic anemia,³² intravascular hemolysis³³ while Chronic toxicity studies describe decane as a tumor promoter in skin cancer.³⁴ Exposure to high concentration of benzene and its methyl-derivatives in polluted air has been associated with bone marrow deficiency, aplastic anemia, and leukemia.^35,36 Long-term exposure to airborne xylene is associated to headaches, irritability, depression, insomnia, extreme tiredness, tremors, hearing disorder,^37,38 impaired concentration and short-term memory loss.³⁹

Information on the magnitude of personal exposures to environmental chemicals^40,41 remains important for the control of related diseases. However, current active samplers (air and biological sampling devices) remain costly and complicated to operate.⁴⁰ Wristbands are a wearable technology that can be used for personalized exposure assessment by passively sampling individuals’ chemical exposures.⁴² Besides being less expensive and easy to use, wristbands have the capacity to provide relevant quantifiable assessment and require less extrapolation compared to the traditional stationary/active and biological methods.⁴² Wristbands are made of silicone which capture chemicals in a process similar to the way the human body absorbs chemicals.¹⁰ The wristbands have the capacity to capture and retain thousands of semi-volatile (SVOCs) and volatile organic compounds (VOCs) including flame retardants, polycyclic aromatic hydrocarbons (PAHs).⁴¹ The PAHs, a class of persistent organic pollutants come from several sources including wood, automobile and industrial activities,^43–45 all common in urban areas. Accurately assessing a person’s exposure to chemicals is essential for determining the impact of environmental exposures on human health.⁴⁶ We therefore conducted a pilot study using silicone wristbands to measure personal exposures to 75 VOCs and SVOCs among fuel station pump attendants, taxi drivers and commercial motorcycle riders in Kampala city, Uganda.

Methods

Study setting

This study was conducted in Kampala, Uganda’s capital city, which borders Lake Victoria. The city is divided into five divisions that oversee local planning: Kampala Central, Kawempe, Makindye, Nakawa, and Rubaga. The population of Kampala grew from 1,189,142 in 2002 to 1,680,600 in 2020.⁴⁷ As Uganda’s biggest commercial center, people are engaged in several income earning activities including retail and wholesale trading, construction, hotels, manufacturing industries, transportation and other businesses.^48,49 Kampala city has high levels of air pollution including chemical pollutants,⁵ which may be driven by among others, the large concentration of industries, and motorists such as motor cyclists, taxis, and a high number of fuel stations.⁴⁹ Individuals involved in the transportation sector are hypothesized to be at greater risk for exposure to VOCs and SVOCs, given their proximity to vehicle exhaust. The study was conducted in Kampala central division, which is the center of business and with potentially higher pollution levels compared to the other four divisions.

Study design and population

This was a cross-sectional study that measured personal exposure to environmental chemicals among fuel station pump attendants (FSPAs), taxi drivers (TDs) and commercial motorcycle riders (CMRs) in Kampala city, central division. We selected these occupations because they were likely to be exposed to chemicals. We used silicone wristbands as a chemical exposure measurement too.⁴² The study participants were above 18 years of age. We employed quantitative data collection methods. The study was approved by the ethics committees of a University in Uganda (HDREC Protocol No 643) and a University in USA (IRB-2019-0070), and registered at the Uganda National Council for Science and Technology (SS 5007), who also authorized the sample transfer. We also obtained permission from the authorities at the selected workplaces. Participation was voluntary and all participants gave written informed consent after being informed of the research objectives, risks and benefits. We handled and stored the data confidentially and only accessible to the research team.

Sample size and sampling procedure

A total of 14 workers were involved in this pilot study. For purposes of a pilot, this sample size was enough to give basic information on personal exposures to environmental chemicals among participants which would inform a bigger study. A similar sample size has been previously used.⁵⁰ Workstations (stages/ranks) for CMRs, TDs, and fuel stations were purposively sampled across major roundabouts/busy roads, where the respondents/workers were selected using convenient sampling on the days for data collection. Participants were found at their workplaces and requested to participate. The wristbands were handed to the participants who were requested to wear them for 24 h a day, over a 5 day period. Overall, the 14 workers (ie, 5 TDs, 5 CMRs, 4 FSPAs) were briefed and encouraged to wear wristbands at all times during the specified period, after which, they were collected by the research team. Participants self-reported high compliance with the study protocol.

Data collection and management

We collected information on socio-demographic characteristics such as education level and occupation characteristics using a paper-based questionnaire. We then linked the demographic information to laboratory data from the wristbands using unique identifiers for analysis purposes. Names and other personal identifiers were not collected except phone contact which was important in following up respondents to collect the wristbands.

Distribution of wristbands and demographic data collection was conducted by experienced research assistants who were trained on the study objectives and research ethics for four days including piloting the demographic tool. The tool was piloted among two taxi drivers who were selected outside the central division, and revisions (majorly related to language translation) were made accordingly. Regarding the handling and storage procedures, participants received wristbands after responding to the demographic tool and being briefed on how to wear them, and who to contact in case of any issues. The wristbands were stored in an airtight bag before they were handed over to the participants for wearing, and after collecting them from participants.

Preparation, storage, and transportation of wristbands

Prior to deployment, silicone wristbands (width: 1.3 cm; inner diameter: 5.8 cm, (https://24hourwristbands.com, Houston, TX, USA) were baked at 300 °C for 150 min, under vacuum (0.1 Torr) in a Blue-M, model no. POM18VC-2 vacuum oven, coupled to a Welch Duo-seal pump, model no. 1405 with sequential nitrogen purges at regular intervals. Wristbands were then stored in sealed metal containers and stored at 4 °C. Single wristbands were repackaged into individual air-tight polytetrafluoroethylene (PTFE) bags for deployment and recovery.³¹

Recovered wristbands were sent to Oregon State University (OSU), where they were cleaned and analyzed using a gas chromatography–mass spectrometry (GC-MS) method. General guidelines for transport in PTFE bags was followed³¹ These guidelines confirm analyte stability for one to two weeks, up to +30 °C, and long-term storage stability at 4 °C to −20 °C for multiple chemical categories. The wristbands were safely transported at ambient temperatures before long-term storage in a freezer, which retains analyte integrity up to 6 months or more for some chemicals).

Laboratory analysis

Detailed laboratory analysis process is described here as used in Senegal⁵¹ and Peru.⁵² Upon return to Oregon State, each recovered wristband was cleaned of particulate matter by rinsing with two rounds of water with resistivity 18 MΩ*cm and once with isopropanol. To assess recovery during extraction of chemicals from wristbands, surrogate standards (1.4 Dichlorobenzene-d4, 9-fluorenone-d8, phenanthrene-d10) were pipetted onto wristbands immediately before extraction. For extraction, each wristband was eluted in 50 ml of ethyl acetate twice, for 12 and 2 h respectively. Extracts were combined and reduced to 1 ml under continuous N₂.

Aliquots of the wristband extracts were spiked with the internal standard perylene-d12 and analyzed with gas chromatography/mass spectroscopy (GC/MS) using an Agilent 7890 A GC coupled to an Agilent 5975 C MS. One ul of the aliquoted extract was injected using a splitless injection onto a DB5-MS column with 99.99% He as a carrier gas and the following oven profile: 35 °C for 4 min, ramping at 8 °C/min to 100 °C, ramping at 16 °C/min to 340 °C and a 340 °C hold for 4 min. There are 77 target compounds quantified in this method. Target analytes with limits of detection (LOD) and limits of quantitation (LOQ) and complete instrument parameters are available in Table S2, as appendix 1 and 2.

Quality control (QC)

We collected blank wristband samples during wristband conditioning, traveling, and cleaning. We collected solvent extraction blanks by performing the extraction process without wristbands. We averaged and subtracted any detected concentrations in the blanks from sample concentrations. Surrogate recoveries ranged from 56% to 93%, with an average recovery of 78%. Instrument concentrations were all surrogate-corrected, and all instrument blanks were below the LOD for all PAHs. During sample analysis, we analyzed instrument blanks and calibration verifications at the beginning and end of each set of wristband samples.

All continuing calibration verifications were verified at ±20% of the true value for >80% of the PAHs. We analyzed continuing calibration verifications approximately every 10 samples and/or at the end of the sample set. If a closing verification did not meet the criteria, we verified the standards and re-ran the samples. Prior to wristband deployment, we extracted and analyzed two wristbands from each batch of conditioned wristbands via GC-MS with a 500 ng internal standard (perylene-d12) and, per our data quality objectives (DQOs), made sure there were less than four discrete peaks over 15 times the response of our internal standard. We also verified wristband color and polymer elasticity to match DQOs. All concentrations in this study are presented in ng/g.

Statistical analysis

We used descriptive statistics to summarize the data. We reported numerical data as medians and interquartile ranges (IQRs) and categorical data as frequencies and percentages in a table. We compared the concentrations of chemicals by age group using Wilcoxon rank-sum tests and by occupation using Kruskal-Wallis H tests. We used robust least squares regression to examine the associations between hours worked and concentrations of common chemicals. We did not perform multivariable regressions because of the small sample size. We conducted the analysis using Stata software version 14 (Stata Corp, TX, USA).

Results

Demographic characteristics of participants

A total of 14 workers, 13 of whom were male, participated in this study. The median age of study participants was 31.5 (IQR: 25–42) years. Taxi drivers had the longest working hours in a week, Median; 96 (Inter quartile range [IQR]: 77–98), followed by commercial motorcycle riders (CMRs), 84 (IQR: 77–91) hours. The median number of hours worked per week was lowest among FSPAs, 15 (IQR: 6–22 h). On the other hand, FSPAs had spent the longest time in their occupation; 15 (IQR: 6–22 years) (Table 1).

Table 1. Demographic characteristics of participants.

	Number of participants
Characteristics	Commercial motorcycle rider (n = 5)	Taxi driver (n = 5)	Fuel station pump attendant (n = 4)	Total (n = 14)
Age in years: Median [IQR]	27 (24–28)	35 (31–42)	38.5 (28.5–49.5)	31.5 (25–42)
Sex: Male, n (%)	5 (100)	5 (100)	3 (75.0)	13 (92.9)
Education level, n (%)
Primary	2 (40.0)	3 (60.0)	2 (50.0)	7 (50.0)
Ordinary Secondary	3 (60.0)	1 (20.0)		4 (28.6)
Higher Secondary		1 (20.0)	2 (50.0)	3 (21.4)
Hours worked per week: Median [IQR]	84 (77–91)	96 (77–98)	72 (66–72)	77 (72–91)
Years in occupation: Median [IQR]	3 (3–3)	10 (5–10)	15 (6–22)	5.5 (3–10)

Note: IQR refers to Interquartile range.

Chemical measurements

A total of 75 chemicals were analyzed for, 33 chemicals (44%) were detected and quantified in at least 50% of the samples while 15 chemicals (20%) were in all the 14 samples. The 15 chemicals including 1,2,3-trimethylbenzene (1,2,3-TMB); 1,2,4-trimethylbenzene (1,2,4-TMB); and 1,3-dimethylnaphthalene (1,3-DMN); 1,6-dimethylnaphthalene (1,6-DMN); and 1-methylnaphthalene (1-MN), which were quantified in all the 14 samples and the chemicals quantified in 50% of the samples are indicated in supplementary file: Table S1. The full list of chemicals analyzed including those detected and quantified in all the wristbands are presented in supplementary file: Table S2 (showing the VOCs and SVOCs).

The median quantification of chemicals per the different occupations indicated that: TDs recorded lowest levels of: 1,2,3-TMB; 1,2,4-TMB and 1,3,5-TMB, which all had highest recordings among FSPAs. Also, 1,3-DMN 70.4 (33–103) ng/g; 1,6-DMN 39.8 (18.4–57.9); 1-MN 32.7 (19.7–51.6) ng/g; and 2-MN 58.3 (39.6–83.5) ng/g; were highest among FSPAs. On average, phenanthrene was highest among TDs 294 (206–305) ng/g although with the highest levels among FSPAs 244 (133.1–346.5) ng/g. Naphthalene exposure in CMRs was more variable, yet on average, levels were highest amongst the FSPAs. Naphthalene levels were on average higher among FSPAs (63.4 (53.1–77.1)) ng/g compared to TDs (31.9 (29.6–35.3)) ng/g and CMRs (46 (44.9–46.7)) ng/g. Similarly, xylenes (m and p) were highest among FSPAs (25.4 (15.4–84.4)) ng/g and lowest in TDs 8.04 (2.64–16.7) ng/g. Of all the three occupations, TDs recorded highest levels of: acenaphthylene 42.6 (31–48.3) ng/g; and all the four decanes (n-Decane; n-Dodecane; n-Pentadecane; and n-Tetradecane). The concentrations of the chemicals confirmed in all wristbands were not significantly different among the different occupations except for naphthalene; H = 6.786, p = 0.036 with highest FSPAs, (Table 2 and Table 3). Further, robust least squares regression showed no significant relationship between concentrations of common chemicals and hours worked (supplementary file: Table S3). The concentrations of chemicals by age group also showed no significant association (supplementary file: Table S4, and S5).

Table 2. Confirmed PAHs levels by occupation.

PAHs, ng/g	Samples with detected levels		Occupation
	No.	Median (IQR)	Commercial Motorcycle rider	Taxi driver	Fuel station pump attendant	Kruskal Wallis test X^2 (p value)
Acenaphthylene	14	31.4 (27.3–42.6)	28.5 (27.3–31.7)	42.6 (31.0–48.3)	26.9 (18.4–42)	2.563, p = 0.278
Acenaphthene	2	53.6 (10.5–96.6)	53.6 (10.5–96.6)	–	–	–
Anthracene	6	41.3 (35.3–61.5)	36 (34.8–41.3)	–	81.3 (61.5–101)	3.429, p = 0.064
Fluorene	14	43.2 (34.2–61.5)	45.8 (40.6–52.2)	36.4 (34.2–54)	48.2 (17.4–94.3)	0.226, p = 0.892
Fluoranthene	14	180 (107–246)	126 (107–138)	255 (246–330)	152.5 (53.7–225)	0.280, p = 0.031
Naphthalene	14	46.4 (35.3–58.8)	46 (44.9–46.7)	31.9 (29.6–35.3)	63.4 (53.1–77.1)	6.786, p = 0.036
Phenanthrene	14	245 (204–305)	226 (204–264)	294 (206–305)	244 (133.1–346.5)	0.280, p = 0.869
Pyrene	13	174.5 (104–280)	104 (91.4–108)	235 (225–355)	236.5(102.8–320)	5.811, p = 0.055

Note: Average concentration (min-max).

Table 3. Common chemicals confirmed in all participants, by occupation.

15 Chemicals confirmed	Total	Average concentration (min-max)
	Median (IQR)	Commercial motorcycle rider	Taxi driver	Fuel station pump attendant	Kruskal Wallis for equality of medians X^2 (p values)
1,2,3-Trimethylbenzene	21.1 (11.8–26.2)	24.4 (18.3–34.2)	11.8 (11.3–20.6)	24.4 (16.0–46.5)	3.266, p = 0.1954
1,2,4-Trimethylbenzene	54.4 (28.5–71.6)	69.1 (44.7–107)	28.5 (24.2–56.1)	62.1 (37.8–141.3)	2.466, p = 0.2915
1,3,5 Trimethylbenzene	13.05 (7.77–16.5)	16.5 (11.3–24.2)	7.77 (6.45–13.6)	14.4 (9.3–30.2)	2.946, p = 0.2293
1,3-dimethylnaphthalene	37 (27.3–47.8)	30.3 (23.7––35.3)	40.6 (34.8–42.2)	70.4 (33–103)	2.443, p = 0.2948
1,6-dimethylnaphthalene	20.9 (14.7––29.4)	15.7 (12.9–17.2)	25.5 (19.7–26.2)	39.8 (18.4–57.9)	2.740, p = 0.2541
1-methylnaphthalene	21.1 (17.5–36.4)	17.6 (16.6–20.7)	21.5 (18.6–22)	32.7 (19.7–51.6)	1.826, p = 0.4014
2-methylnaphthalene	34.6 (29.8–54.2)	31.7 (29.8–35.8)	33.3 (28.7–42.8)	58.3 (39.6–83.5)	2.443, p = 0.2948
acenaphthylene	31.4 (27.3–42.6)	28.5 (27.3–31.7)	42.6 (31–48.3)	26.9 (18.4–42)	2.563, p = 0.2776
n-Decane	72.2 (39.6–93.4)	64.2 (41.5–80.2)	83.4 (51–98.2)	58.0 (22.1–89.9)	0.866, p = 0.6487
n-Dodecane	61.5 (45.6–134)	45.6 (38.5–45.6)	127 (77–140)	101.5 (61.5–210.5)	6.100, p =0.0474
n-Pentadecane	2775 (1580–5390)	1570 (1340–2000)	5230 (2140–8880)	5040 (3425–6770)	6.100, p =0.0474
n-Tetradecane	1355 (457–2400)	457 (396–639)	2450 (1550–3160)	1405 (932.5–2025)	5.126, p = 0.0771
naphthalene	46.4 (35.3–58.8)	46 (44.9–46.7)	31.9 (29.6–35.3)	63.4 (53.1–77.1)	6.786, p = 0.036
phenanthrene	245 (204–305)	226 (204–264)	294 (206–305)	244 (133.1–346.5)	0.280, p = 0.8694
Xylenes (m and p)	17.6 (11.3–31.7)	28 (12.1–51.7)	8.04 (2.64–16.7)	25.4 (15.4–84.4)	4.911, p = 0.0858

Note: Average concentration (min-max).

PAHs and flame retardants

All flame retardants analyzed for were below the limit of detection. A total of 13 PAHs were analyzed for and 8 PAHs detected. Acenaphthene was detected only among CMRs. Of all the PAHs detected, fluoranthene concentrations significantly varied among the different occupations; X² = 0.280, p = 0.0311 with TDs having the highest concentration; Median of 255 (246–330). Similarly, naphthalene concentrations significantly varied among the occupations; X² =6.786, p = 0.036 with FSPAs having the highest concentration; Median of 63.4 (53.1–77.1) ng/g (Table 2).

Discussion

Various VOCs including methylated and non-methylated naphthalenes, and alkanes were quantified across the samples. These compounds are commonly present in fuels,^3,53,54 and get generated during fuel use in vehicles, having a negative impact on environmental and human health. Some chemicals probably or possibly carcinogenic to humans were confirmed including Naphthalene which was found in all samples. Naphthalene levels were expectedly highest among FSPAs; (63.4 (53.1–77.1)) ng/g than in TDs (31.9 (29.6–35.3)) ng/g and CMRs (46 (44.9–46.7)) ng/g. We did not find any studies examining personal exposures to naphthalene in Africa, representing a significant gap in exposure science literature, most probably due to reported limitations of its sampling techniques.⁵⁴ However, Naphthalene, a constituent of petrol, mainly originate from fugitive emissions and motor vehicle exhaust.^53,54 During refueling, motor vehicles often do not follow the ‘switch off engine’ instruction, thus releasing chemicals that may result in heightened FSPAs’ exposure to naphthalene. The reported primary route of exposure is inhalation especially in the vicinity of heavy traffic, and fuel stations.^55–57 Both 1-MN and 2-MN which were also detected have similar characteristics of exposure^25,26 including breathing air contaminated from the burning of fossil fuels. In low-income countries like Uganda, attendants are employed to pump fuel for customers at service stations. They refuel vehicles on a daily basis putting them at risk of exposure to chemicals released from fuels.

Four categories of decanes were analyzed for: n-Decane, n-Dodecane, n-Pentadecane and n-Tetradecane. Decane is identified in the vapor and liquid phases of petrol during vehicle refueling at a pump,⁵⁸ implying that the FSPAs would have higher levels of decanes from the petrol they handle. However, the TDs had the highest levels especially of the n-Pentadecane (2140–8880 ng/g). Participants could have been exposed to consumer products such as wood/furniture, cigarette smoke, plastics and air fresheners, which also contain decanes, besides combustion of kerosene, diesel and petrol.^34,58

Three isomers of trimethylbenzene (TMBs) (1,2,3-TMB, 1,2,4-TMB and 1,3,5-TMB) were identified especially among CMRs and FSPAs which had similar high levels compared to TDs. Vehicle emissions are a major anthropogenic source of TMBs, due to the widespread use of the C9 fraction (liquid pyrolysis products) as a component of petrol⁵⁹ although 1,2,3-TMB, and 1,2,4-TMB exist in the vapor phase in the atmosphere under ambient conditions.⁶⁰ The high levels among FSPAs, was expected since their environment always contains petrol and fuel splashes during refueling, whereas the other two occupation activities involve short visits to the fuel stations. After fueling, there would be minimal exposure from the closed fuel tanks in both cars and motorcycles. The closeness of the fuel tank to the CMRs who are also in the open could explain the higher exposure among them compared to TDs who are protected (remain inside the vehicles). High levels of 1,2,3 TMB and 1,2,4 TMB among FSPAs are similar to a study in Iran that observed concentrations of benzene in the breathing zone of FSPAs at 2–3 times higher than for drivers.⁶¹

The levels of xylenes (m and p) were also higher among FSPAs followed by CMRs. Similarly, 1,3-DMN, 1,6-DMN, 1-MN and 2-MN were highest among FSPAs, therefore, their population may be more at risk compared to the other occupations. The pollutants released from various octane unleaded petrol and diesel fuel which FSPAs closely handle include benzene, toluene, ethylbenzene and xylenes.⁶²

Phenanthrene and acenaphthylene were also common among our study participants. PAHs, are formed via incomplete combustion of fossil fuels, petroleum, and oils. Acenaphthylene was averagely highest among TDs who also worked the longest hours although the chemical concentration level was not significantly associated with the hours worked, probably due to few participants. However, a relationship between working hours, and the detected concentrations of VOCs has been previously reported²³ indicating that TDS experience long periods of exposure to chemicals. Overall, participants in our study were exposed to multiple chemicals, similar to other studies.^23,52,63 Yet, less is known about the health effects of exposure to such multiple VOCs or their combinations.⁶³ Our findings could therefore be used to encourage FSPAs, CMRs, and TDs to take precautions, and concerned authorities and management to institute appropriate control measures to minimize possible health effects related to their working environment. Larger studies are required to assess workers’ exposure to pollutants resulting from the transport industry. Such studies could consider participants wearing the wristbands under long periods of time to facilitate high deposition of chemicals above the detection limits.

Strength and weakness

This pilot study highlighted chemical exposures across three types of transportation workers (commercial motor cyclists, taxi drivers and fuel pump attendants). The findings could indicate potential environmental chemical exposures to individuals living and working within the city since participants wore wristbands for 24 h of all 5 days. We also note no major statistically significant differences between the occupational groups which could be due to this being a small pilot study. Although the study sample size was small, limiting generalizability of findings, we demonstrated the possibility to use wristbands in sampling VOCs in Uganda. All participants reported that they wore wristbands as requested and worked their jobs throughout the specified period. However, assessment of adherence to wearing of the wristbands as required was limited to self-report by the participants, and it is possible that taxi drivers and commercial motorcycle riders could have worked beyond the city during the specified time which could affect the exposure. Taken together, these findings highlight possible environmental chemical exposures among transportation workers within Kampala city whose control is recommended through safety measures such as training of workers, provision and use of personal protective equipment,⁶⁴ and monitoring of exposure to chemicals by the regulatory agencies.^65,66

Conclusion

The participants were exposed to a mixture of VOCs including PAHs and aliphatic compounds most of which have varying effects with some being potential carcinogens. These findings highlight the need for sustainable solutions to protect various workers against the risk of such hazardous exposures. Understanding VOC and SVOC profiles in different job settings is a critical step to identifying effective strategies for reducing occupational exposure levels in the urban environment. Larger studies to generate adequate evidence necessary for control of exposure to various chemicals among workers in Kampala are needed.

Authors’ contributions

Diana Rohlman, Assistant Professor (Sr. Research) College of Public Health and Human Sciences. Oregon State University. Contributions: developed and managed the OSU IRB, provided training materials, contributed to manuscript writing.

Peter Hoffman, Assistant Director Food Safety and Environmental Stewardship Program, Oregon State University. Contributions: Project and sample management, editing and dissemination of Certificates of Analysis from Oregon State, contributed figures and content to manuscript.

Kim A. Anderson, Professor, Environmental and Molecular Toxicology, Oregon State University. Contributions: Study design, technology use of wristband, chemical analysis of wristbands, contributed to manuscript writing.

David Musoke, Senior Lecturer, Department of Disease Control and Environmental Health, School of Public Health, Makerere University, Kampala, Uganda. Contributions: study concept, design, participant recruitment, data collection, and manuscript writing.

Esther Buregyeya, Associate Professor, Department of Disease Control and Environmental Health, School of Public Health, Makerere University, Kampala, Uganda. Contributions: study concept, design, and manuscript writing.

Richard. K. Mugambe, Lecturer, Department of Disease Control and Environmental Health, School of Public Health, Makerere University, Kampala, Uganda. Contributions: study concept, design, and manuscript writing.

Rawlance Ndejjo, Research Associate, Department of Disease Control and Environmental Health, School of Public Health, Makerere University, Kampala, Uganda. Contributions: study concept, design, participant recruitment, and manuscript writing.

John C. Ssempebwa, Senior Lecturer, Department of Disease Control and Environmental Health, School of Public Health, Makerere University, Kampala, Uganda. Contributions: study concept, design, participant recruitment, data collection and manuscript writing.

Edwinah Atusingwize. Research Associate, Department of Disease Control and Environmental Health, School of Public Health, Makerere University, Kampala, Uganda. Contribution: study concept, design, participant recruitment, data collection, and manuscript writing.

Solomon Wafula. Research Associate, Department of Disease Control and Environmental Health, School of Public Health, Makerere University, Kampala, Uganda. Contributions: data collection, statistical analysis, and manuscript writing.

Acknowledgements

We appreciate the support by Makerere University School of Public Health, and the laboratory team at Oregon State University. We appreciate the fuel station pump attendants, taxi drivers and commercial motorcycle riders who participated in this study. The Research Assistants are acknowledged for their support during data collection.

Disclosure statement

Kim A. Anderson and Diana Rohlman, authors of this research, discloses a financial interest in MyExposome, Inc., which is marketing products related to the research being reported. The terms of this arrangement have been reviewed and approved by Oregon State University in accordance with its policy on research conflicts of interest.

Data availability statement

The dataset used during the study is available from the corresponding author on reasonable request.

Additional information

Funding

This study was Funded by Makerere University School of Public Health under the Small Grants Programme, Grant Number: MakSPH-GRCB/19-20/02/02. Wristbands and laboratory analysis was funded by the Food Safety and Environmental Stewardship Program, Oregon State University.