Chronic exposure to a broad spectrum of chemical and physical hazards in the workplace has been consistently linked to alterations in blood cell counts and other hematological indices [1][2]. Industrial chemicals such as benzene, polycyclic aromatic hydrocarbons (PAHs), heavy metals (lead, cadmium, chromium), and organic solvents are known to exert toxic effects on the bone marrow, leading to cytopenias, dysplastic changes, and in severe cases, hematological malignancies [3]. Even at low exposure levels, chronic inhalation or dermal absorption of these genotoxic and myelotoxic agents can produce subtle shifts in blood cell counts before progressing to clinically relevant abnormalities such as anemia, neutropenia, lymphopenia, or thrombocytopenia. Consistent with this, a study of shoe manufacturing workers exposed to benzene at air levels of 1 ppm or less found lower white blood cell (WBC) and platelet counts than in unexposed controls, while progenitor cells were even more sensitive, and genetic susceptibility further modified the risk of benzene-related hematotoxicity [4]. Consequently, monitoring hematological indices in occupationally exposed populations provides a sensitive, non-invasive means of detecting early biological effects and identifying at-risk workers who may benefit from targeted prevention. These effects are particularly relevant in informal work settings, where exposure control is limited and routine medical surveillance is rarely available.

This pattern is further supported by findings from low- and middle-income countries, where studies from West Africa link chronic occupational exposure to petroleum products with measurable hematological changes. In Cape Coast, Ghana, automobile mechanics and sprayers had significantly lower WBC, lymphocyte, monocyte, platelet, and reticulocyte counts than controls, with reduced red cell parameters in mechanics, indicating diminished hematopoietic output [5]. Similarly, in Nnewi, Nigeria, automobile mechanics had lower red blood cell count, hematocrit, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH), along with higher platelet counts than controls, and several indices worsened with longer exposure [6]. Together, these findings suggest that even without overt poisoning, sustained exposure to petrochemicals can produce early blood abnormalities that support routine hematological surveillance in exposed workers. They also underscore the importance of evaluating whether similar effects occur in other informal automotive settings where multiple exposures coexist.

Automobile repair workshops are a pervasive feature of urban and peri-urban landscapes in Benin, as in much of West Africa, and they employ a large, predominantly informal workforce—mechanics, spray-painters, welders, battery recyclers, and apprentices—who face daily exposure to a complex mix of chemical, physical, and ergonomic hazards. Many apprentices begin garage work at an early age, often before 18, which increases their cumulative exposure over the life course and raises the risk that health effects will appear even by middle age. These risks are amplified by poor ventilation, frequent direct skin contact with fuels, solvents and degreasers, and the absence of systematic use of personal protective equipment (PPE)—exemplified by hazardous practices such as hand-washing with gasoline—alongside irregular access to occupational health services. Together, these factors create a particularly high-risk occupational environment for both young trainees and experienced workers. However, previous occupational health research in Benin has concentrated on sectors other than automotive repair, focusing mainly on factors associated with occupational stress and hypertension [7][8]. The systemic hematological consequences of chronic, multi-chemical workplace exposure have not yet been evaluated among automobile mechanics in Benin. This evidence gap limits the ability to design prevention strategies tailored to the specific hazards of informal automotive workshops.

Understanding the relationships between specific work-related factors-such as job specialty, duration of employment, use of protective equipment, and co-exposure to welding or painting activities-and the occurrence of hematological abnormalities is therefore essential. Such understanding can help identify modifiable risk factors, pinpoint workers at greatest risk, guide targeted screening, and support low-cost preventive strategies tailored to the realities of informal automotive repair settings. It may also help distinguish whether observed abnormalities are driven primarily by cumulative exposure, specific tasks, or the combined effects of multiple workshop hazards.

This study, therefore, aimed to characterize the occupational profile of informal automotive mechanics in Benin and to examine whether work specialty, employment duration, PPE use, and multi-trade workshop exposure (co-exposure to welding and painting) were associated with hematological alterations. Specifically, we sought to: 1) describe baseline demographic, occupational and behavioral characteristics by specialty and by employment duration; 2) compare hematological parameters across exposure groups; 3) determine the prevalence of selected hematological abnormalities; and 4) identify independent predictors of these abnormalities using multivariable logistic regression. The results are intended to provide an evidence base for occupational health surveillance and for targeted preventive measures in this neglected workforce.

This cross-sectional study is the first to examine the association between occupational characteristics and hematological abnormalities among informal automotive mechanics in Benin. Our main findings are threefold. First, hematological abnormalities were common and varied significantly by work specialty: microcytic normochromic anemia was most prevalent among diesel mechanics (27.6%), macrocytosis among automobile mechanics (17.9%), and microcytosis showed a borderline difference across specialties. Second, regular use of personal protective equipment (PPE) was strikingly low (19.4%), yet in adjusted regression analysis, it was associated with a marked reduction in the odds of microcytosis (OR = 0.16). Third, older age and longer employment duration were associated with macrocytosis, neutropenia, leukopenia, and thrombocytopenia, while co-exposure to welding and painting (multi-trade workshops) showed a tendency toward increased risk, particularly for thrombocytopenia. Taken together, these findings suggest a pattern of association between occupational exposures and hematological abnormalities in this workforce.

The observed associations are consistent with a hypothesis of cumulative occupational hematotoxicity, but this interpretation remains speculative without direct exposure measurements and longitudinal follow-up. In a workforce exposed daily to mixtures of fuels, solvents, welding fumes, paint aerosols, exhaust particles, and metals, chronic exposure could gradually affect marrow function and red-cell production if a causal relationship exists. Mechanistically, benzene and other aromatic hydrocarbons are metabolized to reactive quinones that induce oxidative stress, DNA damage, and apoptosis in hematopoietic progenitor cells, while heavy metals such as lead and cadmium interfere with heme synthesis and iron utilization. However, our study did not measure these specific agents or their metabolites, so mechanistic claims are not supported by our data. The low prevalence of PPE use is particularly important because it suggests that most workers remain exposed without meaningful protection. The strong statistical association of PPE with microcytic outcomes indicates that even simple preventive behavior may be linked to lower odds of hematological abnormalities. Nonetheless, because PPE use was self-reported and no unexposed control group was available, residual confounding (e.g., healthier workers being more likely to use PPE) cannot be excluded. This is notable because the study population works in largely informal settings where engineering controls and formal occupational surveillance are limited. In this context, the observed abnormalities are unlikely to reflect isolated findings; rather, they may represent the combined effect of repeated low-dose exposure, poor workplace hygiene, and insufficient prevention infrastructure, but this interpretation requires confirmation in longitudinal studies with objective exposure assessment.

Our findings align with a growing body of evidence from low- and middle-income countries. Several studies consistently show that occupational exposure in garages, spray-painting shops, fuel stations, and dust-heavy workplaces is associated with measurable hematological alterations, supporting the idea that blood indices might serve as early biomarkers of exposure-related toxicity. In Pakistan, auto-repair workers and spray painters showed lower RBC and hemoglobin levels, with painters also exhibiting higher WBC, MCV, and packed cell volume; these effects were influenced by smoking, long working hours, poor ventilation, and other workplace conditions, indicating that exposure risk is shaped by both occupational and behavioral factors [12][13]. Recently, Badejo et al. assessed the hematologic profile of workers occupationally and environmentally exposed to petroleum products in Abuja and its environs, and they found that petroleum product exposure was associated with alterations in hematological parameters, with auto mechanics showing particularly notable differences in WBC, Hemoglobin, and platelet counts compared with other worker groups [14]. Similar hematological patterns were reported in Nigeria and Ghana, where automobile technicians had lower RBC and hematocrit and reduced indices with longer exposure, while mechanics and sprayers in Cape Coast showed reduced hematopoietic output, lower RBC and reticulocyte counts, and poor uptake of safety practices [5][6]. Evidence from Ethiopia further supports this pattern: garage workers had lower RBC, hemoglobin, hematocrit, and MCV but higher WBC and platelet counts than controls, and petrol station workers showed significant differences in RBC, hemoglobin, eosinophils, and MCV, with some abnormalities worsening with exposure duration [1][2][15]. Beving et al. reported that long-term low-level exposure to organic solvents among car repair painters and mechanics was associated with reduced erythrocyte counts and increased erythrocyte volume, particularly in painters, compared with unexposed controls [16]. The study also found a shift toward larger erythrocyte size distribution and higher mean platelet volume in the exposed workers, suggesting early hematological effects before clinical symptoms appear [16]. Finally, among automotive body painters exposed to lead, mask use reduced exposure and blood lead levels were inversely associated with RBC, hemoglobin, and hematocrit, reinforcing the potential of simple protective measures to be associated with lower hematological toxicity [17]. Taken together, our results are consistent with international literature and provide the first quantitative estimate of the association between PPE use and hematological outcomes in an informal automotive setting. They also extend prior evidence by showing that these associations are detectable even in a context where multiple exposures co-occur and formal industrial hygiene controls are absent.

One of the most notable findings is the strong statistical association between PPE use and reduced odds of microcytosis. These effect sizes are large enough to be of practical importance if the association is causal, which the current study cannot establish. In our cohort, only 19.4% of workers used PPE regularly, leaving a large majority continuously exposed to agents that may affect bone-marrow function, such as BTEX, PAHs, and heavy metals. The low uptake of PPE is consistent with reports from other West African countries where occupational safety training is rarely provided [5]. However, PPE use in informal settings is often intermittent, incomplete, and poorly standardized; therefore, its apparent protective effect could partly reflect broader safety-conscious work practices rather than PPE alone and could also be influenced by self-report bias. In contrast, working in a multi-trade workshop was associated with lower platelet counts (203.8 vs. 224.2 G/L, p = 0.026) and a trend towards higher frequencies of several abnormalities, although only microcytosis approached significance in regression (OR = 2.17, p = 0.062). The lack of statistical significance may reflect limited power due to small subgroup sizes. Nevertheless, the consistent direction of associations suggests that multi-trade exposure may confer an additional hematological risk. This is important because multi-trade workshops may also have more chaotic work organization, greater overlap of exposures, and fewer opportunities for task-specific protection, which could amplify cumulative toxic burden, if a causal relationship exists.

When considering age and employment duration, older age was independently associated with macrocytosis, neutropenia, and leukopenia. However, the individual adjusted odds ratios for age and employment duration should be interpreted with caution, as these variables are correlated and do not represent fully independent effects. Longer employment duration itself was independently associated with thrombocytopenia (OR = 1.04 per year), consistent with Ibeh et al. [6] who found decreasing platelet counts with longer work duration. The finding that macrocytosis was most common among automobile mechanics (17.9%) might be explained by their longer exposure to organic solvents which have been hypothesized to induce significant effects on hematopoiesis [12]. Conversely, microcytosis was more frequent among diesel mechanics (27.6%) and workers with shorter employment duration, possibly reflecting a different mixture of exposures (e.g., diesel exhaust particulates and metals) that interfere with iron metabolism. An alternative explanation is that some of these patterns may also reflect differences in nutritional status, alcohol intake, or unmeasured inflammatory conditions, all of which can influence RBC indices and should be explored in future studies.

The observed association between PPE use and reduced odds of abnormalities suggests that even simple, low-cost interventions—provision of masks, gloves and coveralls, together with basic training—might yield substantial reductions in hematological abnormalities if the association is causal. Health promotion campaigns should target not only mechanics but also workshop owners and professional associations, emphasizing that regular PPE use may be beneficial even without formal regulatory oversight. Furthermore, the higher risk of anemia and microcytosis among diesel mechanics and the higher risk of macrocytosis among automobile mechanics suggest that different trades may have different exposure profiles. For diesel mechanics, reducing exposure to exhaust particulates and metals (e.g., improved ventilation, banning fuel siphoning) could be prioritized. For automobile mechanics, minimizing skin contact with organic solvents and providing adequate hand-cleaning facilities could potentially reduce macrocytosis. The independent association of employment duration on thrombocytopenia implies that cumulative exposure monitoring might be considered for workers with >20 years in the trade. Regular complete blood count testing could serve as a low-cost screening tool to detect early bone-marrow depression and trigger timely removal from exposure in surveillance context. Finally, the low overall uptake of PPE and lack of safety training highlight the need for policy interventions. Collaborations with professional associations and micro-financing of PPE could be feasible and effective entry points. Beyond individual-level protection, structural measures such as shaded work areas, task zoning, safer solvent substitution, and organized waste handling would likely yield broader risk reduction. Integrating occupational health education into apprenticeship systems may be especially impactful because many workers enter the trade at a young age and remain exposed throughout their working lives.

This study has several strengths. It is the first systematic evaluation of hematological abnormalities among informal automotive mechanics in Benin, filling an important geographic gap. In addition, it is among the few studies to directly compare three distinct specialties within the same informal sector. We collected detailed information on work specialty, employment duration, PPE use, and multi-trade exposure, allowing us to disentangle the associations of different occupational factors. The use of multivariable logistic regression adjusted for key confounders strengthens internal validity. Furthermore, the active engagement of four professional associations facilitated a high participation rate and enhanced representativeness. In addition, the focus on a hard-to-reach informal workforce adds substantial public health relevance, because such workers are often missing from routine occupational surveillance systems.

Several limitations should be acknowledged. First and most importantly, the cross-sectional design and the absence of an unexposed comparison group preclude causal inference. Reverse causation (healthier workers being more likely to use PPE) and residual confounding cannot be ruled out. Exposure assessment relied on self-reported duration and workshop characteristics, without direct air monitoring, which may have introduced non-differential misclassification biasing results toward the null. Small subgroup sizes (diesel mechanics, multi-trade workers) limited statistical power for some comparisons, reflected in wide confidence intervals. We excluded smokers and participants with chronic diseases to reduce confounding, which may limit generalizability to the broader mechanic workforce. We did not measure nutritional status (iron, vitamin B12, folate), which could influence RBC indices independently of occupational factors. Finally, the cross-sectional design cannot capture more severe outcomes such as aplastic anemia or leukemia, which require long-term follow-up. Residual confounding by unmeasured factors such as malaria history, parasitic infections, and prior medication use may also have influenced hematologic values in this setting. Because exposure and outcome were measured at one time point, temporal ordering cannot be established, and the observed associations should therefore be interpreted as hypothesis-generating rather than evidence of causation.

In this first cross-sectional study of hematological abnormalities among informal automotive mechanics in Benin, regular use of PPE was associated with lower odds of microcytic anemia and microcytosis, whereas older age, longer employment duration, and multi-trade co-exposure were associated with higher odds of various cytopenias. The overall uptake of PPE was only 19.4%, representing a missed prevention opportunity. Low-cost interventions promoting mask, glove, and protective workwear use, together with trade-specific exposure reduction, could be considered for improving hematological health, but their effectiveness would need to be confirmed in intervention studies. Longitudinal studies with direct exposure assessment and nutritional biomarkers are needed to determine whether the observed associations reflect causal relationships and to guide targeted screening. Future research should also examine dose-response relationships, biomarkers of oxidative stress and genotype relevant metabolic enzymes (e.g., CYP2E1, GSTM1, GSTP1, GSTT1) to better understand inter-individual variability. Collaboration with professional associations and workshop owners will be essential to translate these preliminary findings into sustainable occupational health improvements in Benin and other West African countries.

The authors express their sincere gratitude to all automotive mechanics for their participation, without which this study would not have been possible. We are particularly grateful to the leaders of the professional associations—Fonton Eloi, Thomas Evedjre, Sandrin Gbaguidi, and Remi Satchoua (AGEPAC), Alfred Dossou-Yovo and Remi Djossou (ABEMA), Serge Messohounsounou (AMDPEMA), and Urbain Kandji (AMECYPAC)—for their dedicated support in participant recruitment, sample collection, and data management. Their commitment has been essential to advancing targeted occupational health screening within Benin. We also gratefully acknowledge Charles Tossou for his invaluable support throughout the study.