Nakagawa N.K.1, Goto D.M.2, Lanca M.1, Yoshida C.T.1, Terra-Filho M.3, Zanetta D.M.T.4, Santos U.P.3
1Faculdade de Medicina da Universidade de Sao Paulo, Physiotherapy, São Paulo, Brazil, 2Universidade Nove de Julho, Physiotherapy, Sao Paulo, Brazil, 3Heart Institute - Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Pulmonology, São Paulo, Brazil, 4School of Public Health, Universidade de São Paulo, Department of Epidemiology, Sao Paulo, Brazil
Background: Manual harvesting is combined with biomass burning in several developing countries. Agricultural biomass burning produces toxic gases and fine particulate matter (PM) that contribute to higher levels of atmospheric pollution. Epidemiological studies assessing the health effects of exposure to these bioproducts on individuals who live in urban areas surrounding agricultural sugarcane fields have shown direct associations between increased PM concentrations related to biomass burning and worsening of cardiopulmonary problems such as increased hospital admissions. However, little evidence exists regarding the health effects of burnt sugarcane harvesting in young healthy subjects never exposed.
Purpose: This longitudinal study investigated whether the effects of burnt sugarcane harvesting would be similar in young healthy workers who had their first 8-monthh exposure (one season) compared with those workers that had worked 1 to 5 seasons before this study.
Methods: Seventy-four healthy subjects (aged 18-45 years) entered into the study. Assessments were performed before and after the harvesting season. We assessed lung function using spirometry, nasal mucociliary clearance (MCC), mucus sneeze clearability, and the mucus contact angle, and we assessed nasal inflammation via cytokine levels and epithelial and inflammatory cell counts.
Results: During the 8-month period of burnt sugarcane harvesting, the median concentration of PM2.5 was 61 µg/m3 (IQR: 41.3-86.8 µg/m3), the mean relative humidity was 72% (SD: 9%), and the mean ambient temperature was 28.1°C (SD: 5.7°C) in the farm area.
Of the 93 sugarcane workers that were recruited, 19 subjects were excluded due to alcohol use or acute respiratory infection, leaving 74 young healthy subjects. The mean exhaled CO concentration was lower than 10 ppm in both the pre- and post-burnt sugarcane harvesting season measurements in naïve (3.0 ± 1.1 and 2.8 ± 1.4 ppm, respectively) and pre-exposed subjects (4.3 ± 1.9 and 4.4 ± 1.7 ppm, respectively). Demographic and clinical data were similar between naïve subjects (n=12) and pre-exposed subjects (n=62) at baseline, with the exception of their FEF25-75% predicted values, which were higher in pre-exposed subjects than in naïve subjects. After 8 months of burnt sugarcane harvesting, both groups had significant decreases in their heart rates, FEV1/FVC ratios and FEF25-75% predicted values as well as significant increases in blood pressure. At baseline, naïve and pre-exposed subjects had similar nasal MCC results. After an 8-month harvesting season, pre-exposed subjects showed impaired nasal MCC with increased sneeze clearability. For NLF samples, no significant differences were found in cytokine concentrations or in the number of cells between naïve and pre-exposed subjects at baseline. After the burnt sugarcane harvesting season, only pre-exposed subjects exhibited significant increases in IL-6 concentrations and in the number of macrophages and ciliated cells.
Conclusion(s): An 8-month period working in burnt sugarcane harvesting increased subjects blood pressure and reduced their lung function. Successive occupational exposures after the initial exposure also induced nasal MCC impairment and inflammation in young healthy subjects.
Implications: Young sugarcane workers are at increased risk of airway defense mechanisms impairment since the first season and with successive exposures they may increase have increased risk to develop respiratory infection, hypertension and decreased lung capacity.
Funding acknowledgements: Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (13/13598-1)
Topic: Cardiorespiratory
Ethics approval: This study was approved by the Ethical Committee Hospital das Clínicas, Faculdade de Medicina da Universidade de Sao Paulo (CAPPesq0282/09).
All authors, affiliations and abstracts have been published as submitted.
