The air we breathe in big cities contains something else besides oxygen. This is the so-called particulate matter, comprised of tiny fragments of chemicals full of heavy metals that cause considerable damage to health, ranging from gastrointestinal disorders to pulmonary or hematological disorders. In the attempt to identify these particulates inexpensively and as an alternative to the conventional equipment used for monitoring the air, researchers from the Federal University of Rio de Janeiro (URFJ) and from the Federal University of Bahia (Ufba) resorted to a bromeliad known as barba-de-velho (Tillandsia usneoides), a species native to Brazilian forests, to study concentrations of heavy metals in the air in the cities of Salvador and Rio de Janeiro. The technique, referred to as biomonitoring of the atmosphere, is still at the experimental stage in research centers in various countries. The study conducted in two capital cities of Brazil – coordinated by biologist Leonardo Rodrigues de Andrade, a professor of the Biomedical Sciences Institute of UFRJ, and pharmacist Nelzair Araújo Vianna, from the Municipal Health Bureau of Salvador – proved that the particulate material in the atmosphere and inhaled by people in both cities contains elements that are toxic for human health.
“We also showed that the Tillandsia usneoides indicates the concentration of metals in the fraction of the most hazardous particulate matter,” says Andrade, who is currently attending a post-doctoral program at the National Institutes of Health (NIH) in the United States. “In addition, we concluded that the main source of these elements in the places where we conducted the studies is related to pollution from automotive vehicles.” According to Andrade, prior to the studies conducted by the researchers, nothing was known about the existence and concentration of heavy metals in the places where the studies were conducted, especially in the city of Salvador. “In a way, our study was the first one to quantify the concentration of metals in the areas where it was conducted,” he says. “Particulate matter is monitored in Rio de Janeiro in the areas where we conducted our research, but heavy metals are not.”
The researchers used the Tillandsia usneoides bromeliad to quantify the existence of five highly toxic elements – copper, chromium, cadmium, zinc and lead – at five sites in the State of Rio de Janeiro – three of which were in the state capital. The research was also conducted in seven sites in the city of Salvador. Two unpolluted sites were also studied as controls: Itatiaia National Park and the town of Cordeiro, in the mountains of the State of Rio de Janeiro. “We chose these metals because they are found in regions that are considered polluted,” says Andrade. Forty five days after the researchers had placed the bromeliads at the chosen sites, they took samples from them to their laboratory, where pieces of the plant were analyzed using atomic absorption spectrophotometer techniques, scanning electron microscopy and X-ray microanalysis.
The research team chose the barba-de-velho bromeliad for the experiments because the physiology of this species is adapted for survival in warm, dry environments. In addition, the species had already been used in several studies in Argentina, Italy, the state of Florida, in the United States, and Germany. In Brazil, in the early 2000s, the species had also been used to analyze the air in São Paulo by the team of professor Mitiko Saiki, from the Institute of Energy and Nuclear Research (Ipen) (see Pesquisa FAPESP nº 104). “Bromeliads are epiphytes that grow non-parasitically on other plants. As these epiphytes have no roots in the soil, they absorb water and nutrients directly from the air, through structures called scales, which cover their body. These scales have tremendous capacity to attract and retain liquid,” Andrade explains. The particulate matter is trapped in the scales and accumulates in proportion to the time that the plant is exposed to air.
In Rio de Janeiro, significantly higher ratios of chromium, cadmium, copper and zinc were found in the biomonitored sites than in the control sites, where the air is not polluted. The cadmium was highest in Jacarepaguá and São Gonçalo. Zinc was the outstanding element: in São Gonçalo, the zinc ratio was as much as 17 times higher than in Itatiaia and Cordeiro. The situation in Salvador was no different. Although the cadmium, chromium and lead had been similar in both cities, the zinc and copper were higher in Rio de Janeiro. “A result of our research in Salvador was the use of the data as the scientific basis for investing in mini air monitoring stations in preparation for the World Soccer Cup in 2014,” says Nelzair. She states that this resulted from their pioneering work in the capital city of the State of Bahia, which mobilized the mass media and environmental authorities. “Prior to this research, Salvador had no data on the condition of the air at the sites where the research was conducted.” The city’s Health Bureau implemented the Inter-Sector Center for Air Quality, coordinated by Nelzair, and recommends that environmental organizations use the Tillandsia usneoides to monitor the air. According to the researchers, the method tested should not replace monitoring stations, which provide more accurate measurements not only of particulate matter but also of other pollutants.
VIANNA, N. A.; ANDRADE, L. R. et al. Assessment of heavy metals in the particulate matter in two Brazilian metropolitan areas by using Tillandsia usneoidesas atmospheric biomonitor. Environmental Science and Pollution Research. v.18, n.3, p. 416-27. 2011.