Occupational Exposure and Health in the Informal Sector: Fish Smoking in Coastal Ghana

Cheryl L. Weyant,1 Antwi-Boasiako Amoah,2,3 Ashley Bittner,4 Joe Pedit,5 Samuel Nii Ardey Codjoe,6 and Pamela Jagger1 School for Environment and Sustainability, University of Michigan, Ann Arbor, Michigan, USA Centre for Climate Change and Sustainability Studies, University of Ghana, Legon, Ghana Environmental Protection Agency (Ghana), Accra, Ghana Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Regional Institute for Population Studies, University of Ghana, Legon, Ghana


Introduction
Fish preservation by smoking is an occupation where workers (primarily women) are exposed to gases and particles from wood smoke for more than 5 h daily (Adeyeye and Oyewole 2016). The scale of this issue is large; we estimate that there are 6 million fish smokers on the West African coast (uncertainty: 0:8-10 million).

Methods
We used a cross-sectional design to explore differences in exposure and self-reported health symptoms between women engaged in occupational fish smoking (fish smokers, N = 308) and those in other occupations, including business-and tradeswomen, fish salters, tailors, hairdressers, and others (controls, N = 152). Households were randomly selected from two small coastal cities in Ghana (Moree and Elmina). Fish smoker and control households were geographically well mixed at an ∼ 2:1 ratio.
A structured survey was used to collect sociodemographic and health symptom data from each household's highest income earning woman. The health questionnaire was modeled on the Ghana Demographic and Health Survey and included 1-y and 2wk symptom recall (Table 1).
The association between exposure and fish smoking was assessed using t-tests and ordinary least squares regression models, controlling for household and individual level variables, including proximity to other sources of combustion pollutants (Table 1). Relationships between health symptoms and fish smoking were tested with v 2 tests and logit models that controlled for the same variables as the ordinary least squares models. Exposure differences due to ventilation and improved smokers were tested with t-tests.
Exposures experienced by fish smokers were higher than from household cooking in nonfishing villages in Ghana. Fish smokers had 24-h CO exposure that was seven times greater than from household cooking in Eastern Ghana (1:1 ppm) (Lee et al. 2019); PM 2:5 exposures were four times greater (129 lg=m 3 ) (Van Vliet et al. 2019). Controls also had higher exposure than typical from cooking (2.6 times greater for CO and 1.5 times for PM 2:5 ) (Lee et al. 2019;Van Vliet et al. 2019). A possible explanation is that fish smoking increases local ambient pollution, raising the baseline exposure of nonfish smokers.
Better ventilation may reduce exposure for fish smokers ( Figure 1D). Women who used open air smokers were exposed to less than half the CO compared with those using indoor smokers (p < 0:01); Flintwood-Brace (2016) also found high indoor fish smoking exposures (18 ± 13 ppm). However, even women who used open air smokers had higher exposures compared with controls (p = 0:01). Counterintuitively, users of improved smokers (with chimneys) had the same level of CO exposure as users of traditional smokers (6:9 ppm and 7:0 ppm, p > 0:05), and higher PM 2:5 (866 lg=m 3 vs. 306 lg=m 3 , p < 0:001).

Symptom Prevalence
Symptoms were more prevalent in fish smokers compared with controls (Table 1). Yet, even for controls, rates were high compared with other populations. For example, the prevalence of difficulty breathing and concentrating were 2 and 3.3 times higher, respectively, compared with biomass cooks in Malawi (Das et al. 2017).

Highly Significant Associations: Eye, Neurological Symptoms, and Burns
Poor eyesight, burning eyes, and dizziness were all strongly correlated with fish smoking and these symptoms were also associated with CO exposure ( Figure 1F). These symptom associations with both fish smoking and exposure are consistent with the hypothesis that occupational fish smoking can cause higher exposure to pollutants, leading to a greater health burden.
Fish smokers were more likely to have burns compared with controls, despite having fewer burns from cooking. Burns reported to be caused by fish smoking tended to be mild (no scars, 70%) compared with those caused by cooking (50%). Three percent of fish smokers had a severe burn in the past year, and 15% had one in their lifetime (83% were from fish smoking).
For headaches, we observed associations with fish smoking and with CO exposure, but only for the 2-wk recall period. We hypothesize that because nearly all women experienced a headache over 1-y, a shorter recall would be required to discern an association. Future studies using self-reported health symptoms should aim to match recall periods with the likelihood of symptoms (e.g., fatigue should have a shorter recall, and coughing blood, longer).
Eye symptoms Poor vision c Note: Each symptom's association with fish smoking was tested using chi squared tests and logit models for 1-y and 2-wk recall periods (odds ratios and 95% confidence intervals shown). The association between each symptom and CO exposure (24-and 8-h) and PM 2:5 were assessed with t-tests.
-, statistical test could not be conducted; Approx., approximated; CI, confidence interval; CO, carbon monoxide; COPD, chronic obstructive pulmonary disease; OR, odds ratio; PM Respiratory symptoms associated with fish smoking did not have a relationship with CO exposure, although they are known to be associated with smoke exposure in other contexts (Van Vliet et al. 2019). We hypothesize that this is because day-to-day exposures were variable and 24-h measures only weakly represent the exposures that drive chronic health outcomes.

Conclusion
Occupational fish smokers experienced an elevated health burden. Rates of self-reported symptoms in fish smokers were higher than those in other occupations, most notably increased rates of poor vision. In addition, because exposure rates in controls were also high, the true health effect estimates of fish smoking relative to a clean environment may be greater than reported here. Fish smoker health may be improved by working in well-ventilated spaces and using improved smokers field tested to verify emission reductions.
The health burden from fish smoking likely impacts millions of workers and is just one of many occupations that use polluting solid fuel combustion. We show here that working with wood combustion for about 5 hours per day has measurable health and exposure associations, even when used outdoors. Millions of workers in low-income countries are engaged in informal sector occupations that use solid fuel for many hours daily (e.g., brick kiln workers, charcoal producers); exposure and health measurements are needed to understand this health burden, especially in the African context.