Environmental Working Conditions, Lung Function and Total Serum Bile Acids of Spray Painters Exposed to Organic Solvents in Ile-Ife, Nigeria

Background. Nigeria has a growing spray painting industry, however, the burden of occupational health problems related to organic solvent exposure among spray painters in Nigeria is under-studied. Objectives. This study aimed to assess workshop characteristics and ambient concentration of total volatile organic compounds (VOCs) in spray painting workshops and to compare lung function status and total serum bile acid levels of spray painters and controls. Methods. A cross-sectional study design was employed to survey 120 spray painters and 120 controls (electronic technicians). A semi-structured questionnaire was used to obtain data on socio-demographics characteristics of the respondents. Weight, height and lung function of respondents were measured. In addition, a checklist was used to survey the spray painting workshops. Total VOC levels were determined in 37 spray painting and 31 electronic workshops. Data were analyzed using Statistical Program for the Social Sciences (SPSS) version 20 and a p-value of <0.05 was considered to be statistically significant. Results. Windows were present in only 5 (13.5%) spray painting workshops and 23 (62%) workshops had a retractable tarpaulin at the entrance. Only 9 (24%) workshops had changing rooms, while fire extinguishers and first aid kits were not present in any of the surveyed workshops. A respirator with filter was sighted in only 1 (3%) workshop. The 8-hour time weighted average concentration of total VOCs in spray painting workshops was 13.4 ppm, which is above the national permissible exposure limits of 1.9 ppm. Forced vital capacity (FVC) percent predicted was significantly lower in spray painters (93.9 ±10.8%) than controls (96.7± 8.2%) (t = −2.326, df=238 p< 0.001). In addition, forced expiratory volume in the first second (FEV1) percent predicted was lower in spray painters (94.6±12.2%) than controls (100.3±9.1%) (t=−4.058, df=238, p=0.002). FEV1/FVC% was significantly lower among spray painters (85.48±8.70%) compared with controls (87.88±6.22%) (t=−2.861 df=238, p= 0.005). Total serum bile acids was significantly elevated in painters (8.71±3.39 mmol/l) compared to controls (4.67 ±2.15 mmol/l) (t=10.358, df=213, p<0.05). Conclusions. Spray painters in the present study conduct their activities in hazardous work settings. More needs to be done concerning workplace regulation and enforcements to ensure that spray painters comply with minimum standards of occupational safety, workplace hygiene and sanitation. Patient Consent. Obtained Ethics Approval. Ethical approval was granted by the Health Research and Ethics Committee of the Institute of Public Health, Obafemi Awolowo University.


Introduction
Nigeria has a growing spray painting industry, as it has one of the highest number of automobiles in Africa, estimated at around 14.6 million as of 2015. 1 Most auto painting in Nigeria is done in workshops and sheds that do not have specialized spraying booths. 2 Spray painters work mainly in the small-and mediumscale sectors of the Nigerian economy and it is a vocation characterized by exposure to chemical hazards, as auto workshops are estimated to generate the highest proportion of small-volume hazardous wastes in the country. 3 The painting procedure itself offers the highest degree of exposure as the paint is aerosolized Since these vapors can be inhaled or absorbed through the skin, individuals who perform this task and do not wear appropriate, personal protective equipment (PPE) such as a respirator or gloves can be adversely affected. 4, 5 Furthermore, considerable inhalation and percutaneous absorption of solvents can occur within minutes of the onset of exposure. Most painting workshops are poorly ventilated and painters often totally enclose their spraying areas during and just after the painting process with make-shift items such as tarpaulin to prevent dust from settling on painted surfaces, and this method exposes spray painters to extremely high levels of chemical hazards. 6 The adverse health effects of organic solvents can be classified according to respiratory, neurotoxic and dermatologic effects. Other less common ill effects include eye irritation and liver and kidney damage. Decreased lung function parameters and the high prevalence of asthma symptoms have also been documented in past studies. 7, 8 A study conducted among workers in a paint production factory in Lagos, Nigeria demonstrated that PPE use was generally low and that workers had higher urine concentrations of heavy metals than controls. 8 This same study observed that 90% of workers reported at least one work-related health symptom. Another study that assessed liver and renal function among paint factory workers in Anambra State revealed that paint factory workers had elevated liver enzymes and higher serum electrolytes concentrations than controls. 9 A lung function assessment among foam industry workers in Onitsha, Anambra State, Nigeria reported lower peak flow readings among workers with presumed exposure to organic solvents compared to controls. 10  For participants less than 18 years of age (apprentices), assent was obtained from the participants, consent was obtained from their parents or guardians and permission was obtained from their supervisors.

Sample Size Determination
The minimum sample size was determined using the following formula for calculating sample size for the comparison of means of two independent groups (Equation

Data Collection
Data were collected from October to December 2016. None of the electronic workshops were located close to spray painting workshops. Data were collected with the aid of an interviewer-administered questionnaire. Information obtained included socio-demographic characteristics as well as medical and occupational history of respondents. A section of the questionnaire was used to record anthropometry such as weight, height and spirometry readings. The questionnaire was translated into Yoruba, which is the local language in the study area and back-translated to English. All subjects were examined privately on site. Measurement of standing height was performed with the aid of a stadiometer which is comprised of a horizontal platform, vertical perpendicular rule and a sliding head board. Subjects were barefooted and stood chest out and erect against the vertical rule with their feet together. Their heels, buttocks and occiput were touching the rule simultaneously while looking horizontally straight ahead. The investigator's eyes were placed level with the headboard to avoid parallax error. Measurements were to the nearest centimeter after sliding down the headboard. All study participants were weighed wearing light clothing and barefooted. Weights were measured using a Camry® weighing scale. The scale was standardized daily before use. Blood pressure was measured using an Accouson's mercury sphygmomanometer (Kris-Alloy, England). Blood pressure was measured in a sitting position with an appropriate cuff size on the left arm.

Spirometry
Pulmonary function tests were conducted using the Spirolab III (MIR Italy). All spirometry tests were conducted within a fixed period (9am-2pm local time) to minimize diurnal variation. 20 Spirometry was performed with participants standing relaxed in front of the apparatus without using a nose clip and with all tight clothing loosened. Before starting the test, the procedure was explained to participants. Subsequently, subjects performed forced expiratory maneuvers from total lung capacity to residual volume to obtain measurements of forced vital capacity and forced expiratory volume in the first second. Research collecting fasting blood samples (early morning without eating) and before commencing the day's work among both spray painters and controls. About 4 ml of venous blood from the cubital vein was withdrawn into plain bottles. Thereafter, the samples were stored in a freezer at -20 0 C for analysis in batches. Laboratory analysis was done using high performance liquid chromatography.

Data Analysis
Data were analyzed using SPSS version 20.0. Mean and standard deviation were used to summarize continuous variables such as age, height, income, FVC, FEV1, and FEV1/FVC, while categorical variables were summarized using frequencies and proportions. Student's t test was used to assess difference in means across the study and control groups. The chi-square test was used to assess the relationship between categorical variables, e.g. smoking status and abnormal spirometry results. Likelihood ratio was used to assess the relationship between categorical variables when more than 25% of the cells had an expected count less than 5. A p-value of <0.05 was considered to be statistically significant.

Results
Socio-demographics characteristics of spray painters and controls are shown in Table 1.
The spray painters and controls were similar in comparable age, height and weight. In addition, years of work experience, monthly income and smoking status did not differ significantly between the two groups.
The physical characteristics of 37 spray painting workshops were assessed and the results are shown in Table 2.   However, almost all workshops had bare earth as the floor material. This is below the standard for designing and constructing spraying booths which stipulates that flooring material be made of a non-permeable, easy to clean surface. 30 Having bare earth as the floor allows for unmitigated soil contamination by chemical agents used in spray painting. Most workshops also had walls made of materials that are not easy to clean, such as wood and tarpaulin.
None of the workshops had mechanical ventilation or independent exhaust as recommended in spray painting workshops. Similarly, most of the workshops had no windows to allow for optimal natural ventilation. Thirty-six workshops (97.3%) had no ceiling. In consideration of economic costs and a desire to aid rapid drying of painted vehicles, many small/ medium scale painters prefer not to install ceilings. However, absence of a ceiling increases temperature in the workshop with an attendant increase in volatility and thus exposure to volatile organic compounds. Another practice that was frequently observed in the surveyed workshops was the use of retractable tarpaulins to prevent dust from settling on the freshly painted surfaces. A consequence of the practice of using retractable tarpaulin at workshop entrances is that there is reduced ventilation and a further increase in ambient temperature due to lack of a ceiling, likely worsening organic solvent exposures for spray painters.
Several other unsafe practices and conditions were also observed. For example, only one in eleven workshops had changing rooms, and only one had an eating area. These conditions have health implications, as contamination of food and clothing may easily occur in the workplace. Furthermore, improper storage of paints and other Ojo et al Spray Painters Exposed to Organic Solvents in Ile-Ife, Nigeria

Table 4 -Distribution of Lung Function Test Results by Occupation and Smoking Status
Research flammable solvents coupled with the absence of fire extinguishers make the workshops vulnerable to fire hazard. The standard safety procedure is that all spray paint workshops should have fire extinguishers due to the fire risks associated with the use of organic solvents. 30 In addition, open dumping and burning of refuse was the most common method of waste disposal across the workshops. These dump sites are close to the workshops and highly inflammable wastes such as containers with dried paints and lacquer are exposed to naked flame. Neither hand washing facilities nor first aid kits were available in the workshops and this also poses significant sanitation and safety risks. Spray painters performed significantly lower on lung function tests compared with controls. In addition, FVC and FEV1 were markedly different between the two groups and this is similar to the findings of Numan in a study conducted among 33 painters in Baghdad, Iraq which reported significant differences in FEV1 and FVC between exposed and nonexposed groups. Algeria who were exposed to organic solvents compared with other workers who were exposed to welding fumes, organic dust and wood dust, as well as non-exposed individuals. 34 The negative correlation between years of experience and FEV1 and FEV1/ FVC readings may suggest an inverse relationship between spirometry and time exposure, which is similar to the findings of Metawally and colleagues in Cairo. 33 However, some studies have demonstrated no relationship between lung function status and solvents exposure. 35, 36 For instance, Ernstgard et al. found no effect of exposure on the pulmonary functions among a group of 10 painters and controls, but this may be due to the use of waterbased solvents among the surveyed painters and the small sample size. 36 In addition, in a study of car painters in Tamilnadu, India, Revathi and Chandrasekhar found no significant difference in FEV1 and FVC readings between exposed and control groups. 37 A major reason for this result was that the study was conducted among young men who had worked between 1-5 years as painters with presumably low solvents exposure. However, spray painters had significantly more obstructive and restrictive ventilatory impairments than controls.
In view of the possibility that smoking may affect lung function status, data were further analyzed based on smoking status. For non-smokers, FEV and FEV1/FVC were significantly different between spray painters and controls, whereas only FVC and %FVC predicted were significantly different among painters and controls who were ever-smokers.
In the present study, total serum bile acids was used as a proxy for organic solvents exposure. The almost twofold higher average value of TSBA among painters compared to controls indicates that TSBA is an effective biomarker for assessing groups of solvent-exposed workers, as suggested in the literature. 16,38 This was similar to findings from a study of 57 Egyptian workers exposed to organic paints, where assessment of serum total bile acids was the only liver function test that was affected in the exposed group without an increase in the frequency of impaired liver-related symptoms, even at short duration of exposure or with low exposure levels. 15 A limitation of the present study was that personal exposure to VOCs could not be quantified, as personal gas samplers were not available. However, the use of a sensitive VOC gas monitor and air sampler in the breathing zone of workers provided a useful estimate of total VOCs in the workshops. Serious respiratory effects (mainly occupational asthma) that may occur among spray painters working in car body repair workshops are generally caused by the diisocyanate hardener (mainly hexamethylene diisocyanate) used in two-component polyurethane paint systems. The present study did not assess the presence of isocyanates in workshops.

Conclusions
Spray painters in Nigeria work in hazardous settings due to the chemicals they work with, the particular environmental conditions in their workshops and poor use of PPEs. Spray painters had significantly lower spirometry test results and elevated TSBA compared to controls. Concentrations of total VOCs across the workshops were clearly in excess of national standards. Future studies to assess individual exposure levels to organic solvents using personal air samplers or bio-monitoring is recommended. More needs to be done in terms of workplace regulation and enforcements to ensure that spray painters comply with minimum standards of workplace hygiene and sanitation. Although relatively expensive, the introduction of waterbased solvents into the Nigerian automobile spraying industry should be encouraged as they are associated with fewer chemical hazards and harmful effects. The provision of standard spraying booths with mechanical ventilation and exhaust systems to minimize organic solvent exposure is an appropriate intervention to safeguard the health of these workers.