Assessment of Incidental Particulate Matter and Associated Occupational Respiratory Health Impairments among Selected Leather Tanning Workers in Pakistan.

Abstract

It is well recognized all over the scientific fraternity that there exists an association of PM with respirational ailments. A growing figure of follow-up experiential studies are being done on occupational environments. This study has made evaluations for leather tannery produced incidental particulate matter and resulting respirational impairments among exposed cohorts. Moreover, the airborne bacterial concentration associated with varied PM sizes, their exposure dose, severities in occupational respiratory forfeits, all for different micro environments within leather tanneries. The highest concentrations of PM10 were observed at sites PU, FU, RHT and B&S. However, the concentrations of PM2.5 were remarkably less compared to PM10 at all the site except for PU, BS, P&S where concentrations of both PM sizes were almost the same. Among smaller fractions, the maximum mass concentration for PM sizes 0.3 and 0.4 µm are found at process site B&S (1.66E+01 and 3.02E+01µg/m3 ). At Wet machine operations (WMO) maximum concentrations of sizes 0.5, 0.6 and 0.8 were measured (5.00E+01, 7.89E+01 and 8.08E+01 µg/m3 ). Production unit (PU) showed maximum concentration of size PM1 as 9.42E+01 µg/m3 . The computed hazard quotient for all the sites was found to be greater than 1, indicating significant respirational risk. For PM2.5 the maximum HQ was estimated for B&S (1.52E+01) and minimum for P&S (1.34E+00). Likewise, for PM10, the maximum HQ was estimated for B&S (5.64E+00) while for FU and P&S the non carcinogenic risk (HQ) was found to be non-significant. Carcinogenic risk of both the particulate sizes did not fall within safe range for any of the process site. The qualitative and quantitative assessment of PM revealed presence of three distinct classes of PM named, biogenic (B&S, S&S, WMO, P&S, FU), geogenic (RHT, B&S, PU, P&S) and incidental anthropogenic tannery PM (PU, FU, WMO, B&S, P&S). Among the elements found in PM, the highest percentages of carbon (PM10 = 4%, PM2.5 = 8%) and Si (PM10 = 25%, PM2.5 = 41%) have been observed. The average concentrations of all the metals including Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, V, As, Be, Ba, Sr, Cd and Pb were well below occupational exposure limits (OELs). The elemental carbon in both PM10 and PM2.5 is less in comparison to OC. The very high OC/EC ratios, indicative of high rate of secondary organic carbon (SOC) formation, supports the high concentrations of SOC. One-way ANOVA revealed significant difference in chemical composition (elements and carbon forms) of both PM sizes at the selected sampling sites. The elements, Cr, Mn, Co, Ni, V, As, Be, Ba and Cd in PM10 showed a direct association with decline in lung function of exposed workers. However, in PM2.5 only two metals, As and Pb, showed this association. There exists an association between increase in carbon content (OC, EC, TC and SOC) in both particle sizes and decline in lung function parameters FEV1, FVC and specially PEF. For both the PM2.5 and PM10, the values of life time cancer risk (LTCR) for only chromium have been found beyond acceptable range. However, for B&S, the hazard quotient for all the metals in PM10 is within safe limit except for Cr, Mn and Al i.e., 6, 2.86 and 1.84 respectively. A similar trend has been observed for these metals in PM2.5. The highest bacterial concentration at RHT (rawhide treatment) and FU (finishing unit), showing 3.6 x 103 and 3.7 x 103 CFU/m3 respectively. Identified bacterial species Corynebacterium include, Ochrobactrum pseudogrignonense, Alcaligenes sp, Neisseria bacilliformis, Enterobacter cloacae, Alcaligenes faecalis and Klebsiella pneumonia. The maximum and minimum values of mass median aerodynamic diameter (MMAD) were recorded as 8.3 µm and as 0.65 µm at B&S and PU respectively. The highest tannery process exposure dose (TPED) was computed as 1516.9 CFU/Kg for FU. The respiratory symptoms among exposed workers in order of incidence were, Dyspnea>phlegm>cough>wheeze=tachypnea, that were significantly synergized during bacterial infections. The respirational health of the working cohorts also varies with a significant difference (p<0.001) in percentage predicted FEV1 and PEF values owed to this exposure variance. The post bronchodilation measurements of FEV1, FVC, and DRSML QAU x PEF represent decline in lung function. Out of identified 26 patients with COPD, maximum was found in RHT. Lung deposition was computed for a PM size range i.e., 0.3 to 10 μm. For all process sites, the highest pulmonary deposition is observed in generation 17-21. The process sites showed greater pulmonic deposition including B&S, S&S and then FU, PU and PS. The maximum deposited surface area, for both bronchial and alveolar deposition, is found to be associated with generation 17-21 in general and particularly generation 19-20 for all the studied micro-environments. However, the maximum total surface area deposited was observed at sites including WMO and FU that was 9x104 um2 /cm3 . Statistically, tannery workers expected pre and post BD % predicted FEV1 and FVC is lower than a control workers expected both pre and post BD % predicted FEV1 and FVC. Being a smoker synergist this impact significantly (p=0.039) for decline in FVC. However, years of smoking did not show synergism. Both restrictive and obstructive patterns of lung function decline have been found among tannery workers. Tannery workers are found to have comparatively reduced mean post work SpO2 and elevated mean post- work blood pressure, and mean pre- and post-work heart rate. However, the oxygen saturation (SpO2) was found to be normal. The mean SGRQ symptoms scores for subject (19.1) and control (15.3) are statistically different (p=0.03) but the correlation between SGRQ and spirometry measures % FEV1, % FVC and FEV1/FVC is negligible. Further, gender-based investigations, animal studies and clinical longitudinal monitoring may be more useful in setting the threshold limits and legitimate control execution criteria at studied tannery works