Biofuels have been considered a cleaner and more sustainable alternative compared to fossil fuels. To reduce the emissions of greenhouse gases as well as local pollutants, several countries are including biofuels in their energy policies. Sugar cane ethanol is one of the most widely used sources of ethanol in Brazil, which has run a program for using ethanol as an automotive fuel since the mid-1970s. Thus, Brazil contains 25% of the total land worldwide that is planted with sugarcane. The state of São Paulo is the largest producer of this crop; between 2001 and 2011, the production of sugarcane grew 121% due to the use of biofuels in cars.
When projecting a future scenario with an increased production, it is important to focus on the health effects associated with the different steps of sugar cane production. Currently, the sugarcane harvest is associated with straw burning for reasons of productivity as well as to avoid contact of workers with the sharp leaves and poisonous animals in the sugar cane plantation. However, the burning process results in a high exposure to smoke, which is still present during harvest.
The environmental impact due to the burning of sugar cane has diminished with the implementation of legislation to suspend the use of burning to use mechanized harvesting as an alternative in São Paulo . These laws have not been extended to the rest of Brazil, where sugarcane plantations are expanding, and in the Central America and Africa, where the burning of sugar cane is still practiced .
Biomass burning is a major source of toxic gases . Several products are generated during this process that result in adverse effects on the health of the exposed population , such as particulate matter, polycyclic aromatic hydrocarbons (PAHs), carbon monoxide, aldehydes, organic acids, volatile and semi-volatile compounds of nitrogen and sulfur, ozone and inorganic chemical species. Taking into account the health effects associated with sugar cane burning, it is important to focus on fine and ultrafine particulate matter (PM10 and PM2.5), which consists of a mixture of liquids, gases and solids deposited on particles such as PAHs, which are derived from an incomplete organic combustion process . PAHs are pollutants that cause mutagenic and carcinogenic effects [6, 7]. In the Brazilian city of Araraquara (an area with high production of sugar cane in São Paulo State), a significant increase in PAHs, especially the benzopyrene fractions of particulate matter (PM10 and PM2.5), occurs during the sugar cane harvest . Populations in areas surrounded by sugarcane plantations are exposed to the particles produced by biomass burning continuously for at least six months to a year, and increased hospital admissions due to asthma occur during these periods [8, 9].
Sugar cane workers are exposed to high levels of particulate matter, thermal overload, and intense physical exertion during the harvest period, and these conditions induce muscle lesions, changes in blood coagulation and heart rate, systemic oxidative stress, and high blood pressure . Sugarcane products have been shown to cause respiratory problems in workers . Furthermore, sugar cane workers are exposed to various genotoxic compounds, including PAHs . Considering the aforementioned evidence, it is important to evaluate genomic instability in sugarcane workers. Micronucleus (MN) assessment is a biomarker test of genotoxic events and manifestations of chromosomal instability that are frequently observed in diseases such as cancer and can thus evaluate the potential risk of disease in exposed populations . The MN test in blood lymphocytes and buccal mucosal cells is widely used to assess the extension of chromosomal genetic alterations promoted by the exposure to environmental toxicants [13–15]. The aim of the present study was to evaluate the MN frequencies in blood lymphocytes and exfoliated buccal cells of sugar cane workers during the harvest season.