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Revista Pan-Amazônica de Saúde

Print version ISSN 2176-6223On-line version ISSN 2176-6223

Rev Pan-Amaz Saude vol.8 no.4 Ananindeua Oct./Dec. 2017

http://dx.doi.org/10.5123/s2176-62232017000400005 

OPINION ARTICLE

"Watch your step": dangers of soil contamination*

Flavio Manoel Rodrigues da Silva Júnior1 

1Universidade Federal do Rio Grande, Instituto de Ciências Biológicas, Rio Grande, Rio Grande do Sul, Brasil

It is indisputable that, considering the amount of water on our planet, this could be called Planet Water. However, we cannot close our eyes to the nearly 30% of the earth's surface that gives its name to the planet, which is home to the more than 7.5 billion human beings and an important portion of our biodiversity. It is on our ground, on our soil, that our buildings, highways, railways are built; it is in our planet that most of the food is cultivated or created for our consumption; and where we spend most of our lives.

The soil compartments depend on different processes that can reduce its quality, such as erosion, desertification, flooding, presence of pathogens and parasites and contamination by chemical substances. All these processes seem to have a close connection with anthropogenic activities; but, on the other hand, they are also able to affect the quality of life of the human beings in a negative way. The chemical contamination of the soil stands out among these processes, not because it is the most aggressive or the one that causes the greatest damage to the soil, but because it is the quietest and invisible one. Certainly, a mother would prevent her child from playing in the sand in order not to catch germs, parasites, bacteria, chigoe fleas; never to avoid lead poisoning, selenosis or intoxication by any other chemical element, which may be present in high concentrations in the soil.

Although soil is the source and/or deposit of many chemical contaminants, the number of studies investigating the degree of soil contamination and its ecological effects and in human health, this contamination is still much lower than pollution of the aquatic environment, for example. Anyone can come to the same conclusion by searching for some database of scientific articles using the indexing terms corresponding to this subject.

From the point of view of the legal protection of environmental compartments and based on the resolutions of the National Environment Council (CONAMA), although Resolution No. 420/20091 on the protection of soil and groundwater quality, is more recent than Resolution No. 003/19902, which provides on air quality (it is necessary to update this last Resolution), it has some feasibility problems. Perhaps the main one is to establish quality reference values (VRQs) by the state environmental agencies and the Federal District.

In CONAMA Resolution No. 420/20091 suggests what kind of soils will follow the guidelines for the management of contaminated areas, its suggestion occurs through the categorization of soils in different soil quality classes, based on the concentration of chemical substances, establishing four classes in increasing order of contamination: Class 1, Class 2, Class 3 and Class 4. This framework is based on guiding values: VRQs; prevention (PV); and research (VI). VI is the concentration of a particular substance in the soil which, at high levels, presents potential risks to human health. VP is the limit value of a specific substance, so that it is able to sustain its main functions and has been established based on phytotoxicity analysis and ecological risk assessment. VRQ is the concentration of a specific substance that defines the natural quality of the soil. The first two values were determined in that Resolution; but the VRQs would be established by the competent state and environmental agencies of Federal District within a four-year term after that Resolution was published; a new deadline was subsequently set, December 2014. Until 2016, of all state and Federal District environmental agencies, only five had established their own VRQs3. Even for these States, the number of chemicals contemplated was reduced.

Legal sphere aside, it is important to mention other aspects about exposure to soils and their chemical contaminants, as well as their adverse effects on living organisms. The first relevant data to be mentioned, and that few people know, is that the United States Environmental Protection Agency estimates the rate of involuntary ingestion of soil (soil + dust) in the order of: 100 mg/day, for children from 0 to 6 months of age; 200 mg/day for children from 6 months to 12 years of age; and 100 mg/day for individuals from 12 years of age4. In a quick account, considering a life expectancy of approximately 80 years, we calculate that each human being involuntarily eats almost 3.5 kg of soil during his lifetime. This means that, hypothetically, a person who spends his whole life in a soil with a concentration of 300 mg/kg of lead (permitted by CONAMA Resolution for residential soils) involuntarily ingests, just by living and breathing in that environment, more than 1 g of lead throughout life. Does it sound irrelevant? This is equivalent, on average, to 34.3 µg/day of lead. Here it is important to mention that the Food and Drug Administration, the U.S. food safety control agency, sets the maximum level of lead exposure caused by food at 6 µg/day5.

In 2014, we published a study that related soil intake from areas impacted by coal activities with the mutagenic risk obtained through the established by Ames test6. The amount of soil required to double the rate of spontaneous mutation and the time required for this rate to be reached was calculated (using the value of 200 mg/day of involuntary intake of soil in children). The results revealed that exposure to soils, for a period between 0.6-3 days, was already sufficient to double the rate of spontaneous mutation, since these rates were obtained with values ranging between 129.3 and 600 mg of soil. Among the soil collection areas of this study, there were public parks, which warns us about the mutagenic risk to children may be exposed, by the simple and innocent fact of playing in a park or in a place near their home.

Another study investigated the impacts of exposure to soils in public squares contaminated by mercury. During 120 days, Wistar rats were exposed to soil leaching and, after this period, hematological, physiological and mainly behavioral alterations were observed. After this chronic exposure, some rats began to lose mobility of the posterior trunk, compromising their locomotion. Obviously, this result cannot be overtaking to a scenario of human exposure to these soils, but it is warning to the danger of chronic exposure to urban soils contaminated by mercury7.

A number of other experimental studies have revealed adverse effects resulting from exposure to contaminated urban soils, causing genetic damage8, physiological9 and reproductive problems10. As mentioned earlier, we must be careful in going beyond these scenarios, but such studies reveal the dangers of exposure to soil contaminated by chemical substances and to be more careful where we step on.

Our close relationship with the soil highlights the need to be careful with this environmental compartment, and the studies alert us to the progressive decrease in soil quality and the potential invisible risks to which we are vulnerable to. The environmental agencies need to ensure compliance with the legal duties of polluters and improve, day by day, the mechanisms we have for the maintenance of environmental quality. The society also needs to be aware about it, because "what is pollutant is invisible to the eye".

REFERENCES

1 Brasil. Ministério do Meio Ambiente. Conselho Nacional do Meio Ambiente. Resolução Nº 420, de 28 de dezembro de 2009. Dispõe sobre critérios e valores orientadores de qualidade do solo quanto à presença de substâncias químicas e estabelece diretrizes para o gerenciamento ambiental de áreas contaminadas por essas substâncias em decorrência de atividades antrópicas. Diário Oficial da União, Brasília (DF), 2009 dez 30; Seção 1:81-4. [Link] [ Links ]

2 Brasil. Ministério do Meio Ambiente. Conselho Nacional do Meio Ambiente. Resolução Nº 003, de 28 de junho de 1990. Dispõe sobre padrões de qualidade do ar, previstos no PRONAR. Diário Oficial da União, Brasília (DF), 1990 ago 22; Seção 1:15937-9. [Link] [ Links ]

3 Reis FO, Martinez EA, Silva Júnior FMR, Lima ACR. Análise dos dispositivos legais nos estados brasileiros perante a Resolução 420/2009. Âmbito Jurídico, Rio Grande [Internet]. 2017 mar [citado 2017 out 13];XX(158). Disponível em: Disponível em: http://ambito-juridico.com.br/site/?n_link=revista_artigos_leitura&artigo_id=18630 . [ Links ]

4 U.S. Environmental Protection Agency. Office of Research and Development. Update for chapter 5 of the Exposure Factors Handbook: Soil and Dust Ingestion. Washington: United States Environmental Protection Agency; 2017. (EPA/600/R-17/384F). [Link] [ Links ]

5 U.S. Department of Health and Human Services. U.S. Food & Drug Administration. Questions and answers on lead in foods [Internet]. Silver Spring (MD): U.S. Food & Drug Administration; 2017 [cited 2017 Oct 14]. Available from: Available from: https://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm557424.htm . [ Links ]

6 Silva Júnior FMR, Vargas VMF. Tools used to estimate soil quality in coal combustion waste areas. An Acad Bras Cienc. 2014 Jun;86(2): 769-76. Doi: 10.1590/0001-3765201420130038 [Link] [ Links ]

7 Muccillo-Baisch AL, Mirlean N, Carrazzoni D, Soares MCF, Goulart GP, Baisch P. Health effects of ingestion of mercury-polluted urban soil: an animal experiment. Environ Geochem Health. 2012 Feb;34(1):43-53. Doi: 10.1007/s10653-011-9389-z [Link] [ Links ]

8 Garcia EM, Silva Junior FMR, Tavella RA, Cruz CG, Baisch PRM, Muccillo-Baisch AL. Genotoxicity in the offspring of rats exposed to contaminated and acidified experimentally soils. Water Air Soil Pollut. 2017 Jul;228:254. Doi: 10.1007/s11270-017-3440-3 [Link] [ Links ]

9 Silva Júnior FMR, Silva PF, Garcia EM, Klein RD, Peraza-Cardoso G, Baisch PR, et al. Toxic effects of the ingestion of water-soluble elements found in soil under the atmospheric influence of an industrial complex. Environ Geochem Health. 2013 Jun;35(3):317-31. Doi: 10.1007/s10653-012-9496-5 [Link] [ Links ]

10 Garcia EM, Silva Junior FMR, Soares MCF, Muccillo-Baisch AL. Developmental effects of parental exposure to soil contaminated with urban metals. Sci Total Environ. 2015 Jul;520: 206-12. Doi: 10.1016/j.scitotenv.2015.02.088 [Link] [ Links ]

*Opinion article written by Speaker for the II International Scientific Meeting of Instituto Evandro Chagas, held from October 25 to 27, 2017, in Ananindeua, Pará, Brazil. All the articles of this modality were analyzed by the Scientific Committee of the Event and, later, by the Editors of RPAS.

Article originally published in Portuguese (http://dx.doi.org/10.5123/S2176-62232017000400005) Translated by: Patrícia Campelo Haick

Received: October 14, 2017; Accepted: October 18, 2017

Correspondence / Correspondência: Flavio Manoel Rodrigues da Silva Júnior Universidade Federal do Rio Grande, Instituto de Ciências Biológicas Av. Itália km 8. Campus Carreiros - CEP: 96203-900 - Rio Grande, Rio Grande do Sul, Brasil - Tel.: +55 (53) 3233-6633 E-mail: f.m.r.silvajunior@gmail.com

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