Trace Elements and Security of Foods Produced in Urban Community Gardens, Curitiba, PR, Brazil

doi:10.21203/rs.3.rs-2231410/v1

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Trace Elements and Security of Foods Produced in Urban Community Gardens, Curitiba, PR, Brazil

https://doi.org/10.21203/rs.3.rs-2231410/v1

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Urban gardens have emerged as a new global tendency for supporting food security, and has therefore become the focus of diverse studies and attracted the attention of public administrations as an option for sustainable food production. Vegetable crops cultivated under conditions of high exposure to contaminants found in large urban centers, however, tend to accumulate toxic compounds, such as, trace elements, and insert them into human foods and the trophic chain. We therefore evaluated the food security of vegetables (lettuce and collard greens) produced in urban gardens in the Metropolitan region of Curitiba City (Brazil) in terms of the presence of trace elements. Assays were performed in plants harvested from four urban gardens as well as an agroecology site (control). We also assayed for trace elements in the garden soils and the irrigation water used for their production. Both the soils and the irrigation waters had trace element concentrations within the maximum recommended limits, and were therefore not vehicles of contamination. Similarly, trace element concentrations identified in the biomasses of lettuce and collard greens plants grown in the control area, as well as the four urban gardens, were below the maximum limits recommended for leafy vegetables. The vegetables produced in the urban gardens and the agroecology area are considered safe for human consumption.

Urban agriculture

food security and nutrition

trace elements

Lactuca sativa

Brassica oleracea

Urban agriculture has attracted official attention as a method of promoting sustainable food production and food security (Veenhuizen 2006). Those goals accrue social importance and demonstrate a concern for food quality in urban areas in light of atmospheric pollution and soil contamination by trace elements that could accumulate in cultivated plants and represent risks to human health (Dala-Paula et al. 2018).

Plants require both macro- and micronutrients for their growth and development. Although trace elements such as copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), and zinc (Zn) are essential to plants, at high concentrations they can become toxic – as are nonessential trace elements such as arsenic (As), cadmium (Cd), chrome (Cr), and lead (Pb). Similarly, the excessive ingestion of those same elements can be dangerous to humans (Emamverdian et al. 2015; Gupta et al. 2019a). The toxicity of trace elements to humans will depend on the manner in which a person is exposed to those elements, the types and qualities ingested, as well as the levels of physiological disequilibrium caused by them, including nutritional imbalance and oxidative damage to cell components (enzymes, DNA, lipids, and proteins) (Gupta et al. 2019b). Toxic levels of trace elements can cause dementia in adults, intellectual deficiencies in children, disturbances of the central nervous system, kidney and liver diseases, sleeping disturbances, and even death (Emamverdian et al. 2015; Gupta et al. 2019a).

Concerns about access to food resources by many sectors of the population have increased in recent years, especially in terms of the poorest citizens, and has been accentuated by the Covid-19 pandemic. Some indicators cited in a report issued by the Food and Agriculture Organization of the United Nations (FAO) concerning food security are quite alarming: (a) in 2020, in the midst of the pandemic, global hunger increased after previously remaining stable for five years; (b) in just a single year poor levels of nutrition increased from 8.4 to 9.9%; (c) between 720 and 811 million people in the world experienced hunger in 2020; (d) hunger affected 21% of the population of Africa, 9.0% of Asia, and 9.1% of Latin America and the Caribbean area; (e) more than half of the under-nourished people on the planet live in Asia (418 million), and more than one third live in Africa (282 million); (f) the global prevalence of moderate to severe food insecurity had increased very little until 2014, but the numbers related to food insecurity in 2020 alone corresponded to those of the previous five years considered together; (g) nearly one in three persons in the world (2.37 billion) were not able to adequately feed themselves in 2020 – an increase of almost 320 million people in just a single year; (h) the most elevated increases in moderate to severe food insecurity were identified in Latin America, the Caribbean region, and Africa (FAO/WHO 2021). The pandemic therefore revealed the absolute necessity of improving food security in large cities (FAO/WHO 2021).

Interest in urban agriculture has increased considerably in recent decades, principally in developing countries (Savi et al. 2019). Urban agriculture represents an important public policy to guarantee access of the poorest members of society to food resources, and contributes to bettering community and family relationships in large urban areas (Langemeyer et al. 2021). Community gardens have therefore taken on political relevance in Brazil in terms of fighting poverty and improving community food security (Branco and Alcântara 2011), favoring the useful occupation of urban spaces (Pinto and Ramos 2008), and providing social, cultural, economic, and environmental benefits. There have been very few studies, however, focusing on the security of food produced in urban gardens in Brazil, especially in terms of possible accumulations of toxic trace elements. Urban gardens may occasionally be established in areas with high concentrations of trace elements in the soil, air, or water – which would favor their accumulation in cultivated plants and their insertion into human diets (Gupta et al. 2019b; Pan et al. 2016).

There can be numerous emission sources of trace elements in urban centers, including industries and the heavy circulation of automobile traffic (Demirezen and Aksoy 2005; Islam et al. 2021). França et al. (2017) reported a significant increase in Cd, Pb, Ni and Zn concentrations in plants growing in the metropolitan region of Recife City, Pernambuco State, Brazil. Those authors noted that the high levels of those elements in plants were related to particulate emissions in the atmosphere that spread those contaminants to the air, water, and cultivated soils (França et al. 2017), as they can be transported significant distances once liberated to the atmosphere (Demirezen and Aksoy 2005; Gupta et al. 2019a; Hanke et al. 2010).

Plants grown in urban gardens can evidence high levels of trace elements in their biomass when cultivated in localities near pollutant and residue sources (Drabek et al. 2020). Additionally, vegetable crops cultivated in urban areas can become contaminated with trace elements due to their incorporation to substrate through managements such as organic matter and chemical fertilization and/or through the use of agrochemicals (fertilizers and agricultural defensive products) (Bati et al. 2017; Radulescu et al. 2013). The constant monitoring of trace elements in plant material derived from urban gardens will therefore be necessary to minimize public health risks (Alfaro et al. 2017).

The creation of the Municipal Secretary of Supply (SMAB) in Curitiba City in the 1980s stimulated urban agriculture for food production as a public policy. The Garden Program (Programa Lavoura) was established in 1986 to address social problems and to diminish criminality and the irregular occupation of urban areas and, by 2018, 24 urban gardens had become established (Yonegura and Silva 2021). By 2018, the number of urban gardens in Curitiba and the surrounding metropolitan region had increased to 93 (Lima and Gadens 2019); there are currently more than 100 community gardens supported by the urban agriculture policies of the Mayor’s Office of Curitiba (PMC). In addition to producing garden vegetables, public policies of administering urban spaces have facilitated the maintenance of the electrical transmission infrastructure, discipline the occupation of open public spaces, and avoided the accumulation of waste and construction residues (PMC 2019).

Despite the existence of public policies to encourage the development of urban and peri-urban agriculture free from toxic agrochemicals in Curitiba City and the Metropolitan region, very few studies have been undertaken focusing on the safety of the food products grown in those gardens, principally in terms of trace element accumulation. The objective of this work was therefore to evaluate the concentrations of both essential and toxic trace elements in Lactuca sativa (lettuce) and Brassica oleracea (collard greens) plants cultivated in four urban gardens in Curitiba. Those species were chosen because they are among the leafy vegetables most commonly cultivated in community gardens and belong to the families Asteraceae and Brassicaceae respectively – groups known to be potential bioaccumulators of trace elements (Dala-Paula et al. 2018; Gupta et al. 2019a). Lactuca sativa (lettuce) is one of the most economically important leafy vegetable crops in the world (Shatilov et al. 2019) Brassica oleracea (collard greens), in turn, is considered as one of the world’s healthiest vegetables (Chen et al. 2014), and it plays an important role in human nutritional balance (Šamec et al. 2019). The present work therefore sought to evaluate the levels of security of the vegetables produced in urban gardens in Curitiba City in Paraná State, Brazil, and the surrounding metropolitan region, in terms of the presence of trace elements and to identify possible routes of transfer of those elements to the plants.

2.1 Study areas

The urban gardens chosen to be evaluated were selected considering the following aspects: (a) the presence of L. sativa (lettuce) and B. oleracea (collard greens) plants; (b) the use of those areas; (c) their location in areas possibly subject to negative impacts due to urbanization (receiving rainwater runoff from asphalt and their proximity to rail yards or vacant lots with histories of the accumulation of trash and discarded building material). Collections in those areas were authorized by the Municipal Secretary of Food Security and Nutrition (Secretaria Municipal de Segurança Alimentar e Nutricional (SMSAN) of Curitiba City.

The four urban gardens selected for the present study are denominated here as: Horta Marumbi 1 (HM1), Horta Marumbi 2 (HM2), Horta Pantanal (HP), and Horta Esquina Verde (HEV). The Horta do Centro Paranaense de Referência em Agroecologia (HCPRA) garden, located in an Environmental Protection Area (APA) in Pinhais City, PR, Brazil, in the metropolitan region of Curitiba (Table 1) was chosen as a control as that garden follows the precepts of agroecology. Soil, water, and plant collections were undertaken between the months of June and July/2021 (Table 1).

Table 1. Urban gardens located in Curitiba City and the surrounding metropolitan area in Paraná State, Brazil, with their respective coordinates, use histories, and collection dates.

Gardens	Coordinates	Use history	Collection dates
Marumbi 1 (HM1)	25°28'59.1"S 49°12'16.5"W	Vacant site used for dumping solid residues and used and discarded building material (in the more elevated section)	2021/06/28
Marumbi 2 (HM2)	25°28'58.8"S 49°12'13.9"W	Vacant site used for dumping solid residues and used and discarded building material (in the lower section)	2021/06/28
Pantanal (HP)	25°32'17.3"S 49°14'01.1"W	Area located next to a rail yard and repair building for locomotives, with regular train traffic	2021/06/30
Esquina Verde (HEV)	25°24'06.6"S 49°15'00.3"W	Vacant site impacted by rainwater runoff from asphalt, located along the side of a heavily used road	2021/07/02
Centro Paranaense de Referência em Agroecologia (HCPRA)	25°22'53.9"S 49°07'36.6"W	Located in the Iraí Environmental Protection Area (APA), with a history of gardening using agroecology techniques	2021/06/23

2.2 Characteristics of the gardens

The urban gardens consisted of plots cultivated using techniques and management practices oriented by professionals from the Urban Agriculture Unit (UAU) of Curitiba City (SMSAN 2020), with emphasis on subsistence agriculture where families are directly responsible for the management and production of the vegetable crops (Oliveira et al. 2021; Silva 1999). Vegetables that exceed consumption needs can be commercialized in local establishments as additional income sources.

The management of those gardens are based on organic agricultural techniques, with the recycling of organic material and without the use of fertilizers, pesticides, or herbicides (Oliveira et al. 2021; Souza 2005). The soils in the areas where the gardens were planted usually demonstrated some level of degradation, with the O and A horizons deteriorated or absent. Therefore, to make cultivation possible, topsoil was initially imported (first quality, sieved, dark, and free of impurities, woody material, seeds, weeds, roots, clods and clay, and without chemical or biological contaminants; approximately 8 m³ per bed). Lime is added every two years, and agricultural products are prohibited following the legislation covering organic agriculture; the planting beds are turned over after each planting cycle to improve aeration.

The HCPRA garden was installed in the Iraí APA, where Organosols predominate. The horticultural practices adopted there include fertilization with vermicompost, mixed plantings in the same bed, crop rotation (family, genus, and species), control of non-vegetable crops through weeding at first and then covering with mulch, micro-spray irrigation, fallowing beds, and recycling organic material (IDR-PR 2021).

2.3 Soil evaluations (culture substrates)

Soil samples were collected at a depth of 0 – 20 cm, where the roots of vegetable crops usually grow and develop. The numbers of beds sampled varied among the different gardens in light of the availability of L. sativa (lettuce) and B. oleracea (collard greens) plants: four beds in HM1 and HM2; three beds in HP; two in HP; and one in HCPRA, with 10 samples being collected in each bed.

After collection, the soil samples from each bed were mixed, and approximately 500 g was brought to the laboratory. The material to be assayed was dried at 60^oC for 24 hours, macerated using a mortar and pestle, sieved (0.2 mm), and the concentrations of the trace elements As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were evaluated using EPA 3051A protocols (Kinuthia et al. 2020).

Triplicates of 250 mg of soil from each sample were homogenized in concentrated nitric acid (HNO₃) and concentrated hydrochloric acid (HCl) (3:1). After 20 minutes of pre-digestion at room temperature, the samples were heated in a microwave oven (Mars Xpress 6, CEM). The determinations of trace element concentrations were made using inductively coupled plasma atomic emission spectroscopy (ICP-OES) (USEPA 2007). SpecSol ®, 1.000 mg.L^-1, standards were used to guarantee the quality of the ICP-OES analyses.

2.3 Evaluation of the irrigation water

A volume of 500 mL of irrigation water was collected from each garden, transported in sterile borosilicate flasks, and conserved under refrigeration. 2 mL of concentrated HNO₃ and 0.4 mL of concentrated HCl were added to 18 mL water samples (in triplicate) from each garden. After 20 minutes of pre-digestion, the samples were heated in a microwave oven (Mars Xpress 6, CEM). The presence and concentrations of the trace elements As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined using the EPA 3015A protocol (Kinuthia et al. 2020).

2.5 Analyses of plant biomass

The choice of L. sativa (lettuce) and B. oleracea (collard greens) plants for examination in this research project was based on three criteria: 1) those leafy vegetables are widely cultivated in community gardens; 2) their short life cycles; and 3) the availability of sufficient biomasses of those plants in each urban garden. Samples from 10 plants (their leaves – corresponding to the edible portion of the plants) were collected in each community garden. After washing in distilled water, the leaves were dried at 55° C for 72 hours until reaching a stable dry weight. The samples were then homogenized and ground in a Willye type mill (model STAR FT-60 Macro). Three 200 mg sub-samples of each plant species from each garden were used to determine the presence and concentrations of the trace elements.

The plant material was digested by adding 4 mL of concentrated HNO₃ with 1 mL of 30% (v/v) hydrogen peroxide (H₂O₂). After pre-digestion for 30 minutes at room temperature, 8 mL of H₂O Milli-Q® was added and the samples digested in a microwave oven (Mars Xpress 6, CEM) using step-up heating for 20 minutes at 1800 W to increase the solution temperature to 180° C; that temperature was maintained for 15 minutes, and the samples then cooled for 15 additional minutes. After cooling, the material was quantitatively filtered into 25 mL graduated flasks through blue ribbon slow filter paper. The presence and the concentrations of the trace elements As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined using the ICP-OES protocol (Andrade et al. 2009; Carmo et al. 2000; Sadzawka et al. 2004).

2.6 Data analysis

The data were submitted to tests of normality (Shapiro-Wilk) and homogeneity (Bartlett). In the absence of normality, the data were transformed. The data were then evaluated using analysis of variance (ANOVA). When differences were detected by ANOVA, the means were compared using the Tukey test (P < 0.05). The statistical evaluations were performed using JMP® version 13 Software (SAS Institute Inc., Cary, NC, USA).

3.1 Borderline concentrations of trace elements

The maximum limits tolerated for ET in different matrices are shown in TABLE 2. These limits were used as a guide to establish the presence of ET in concentrations above those allowed in the samples collected in urban gardens.

Table 2. Maximum tolerated limit for analyzed trace elements for soil, water and leafy vegetables in different countries.

Organization or country	Variable	Maximum tolerated limit for the analyzed trace elements (mg.Kg^-1or mg.L^-1)									Source
Organization or country	Variable	As	Cd	Cr (V)	Cu	Fe	Mn	Ni	Pb	Zn	Source
Brazil	Potable water	0.01	0.005	0.05*	2	2.4	0.1	0.07	0.01	ni	(Brasil 2009) (Brasil 2011) (Brasil 2013) (Brasil 2021)
	Soil	15	1.3	75*	60	ni	ni	30	72	300
	Leafy vegetable	0.3	0.2	ni	ni	ni	ni	ni	0.3	ni
USA	Potable water	0.01***	0.005	0.1*	1.3**	ni	0.05	0.02	0.015***	5****	(USEPA 2021) (USEPA 2005a) (Kinuthia et al. 2020)
	Soil residential	ni	0.48	11	ni	ni	ni	72	200	ni
	Vegetable	ni	0.2	2.3*	ni	ni	ni	ni	0.3	ni
FAO / WHO	Natural water	0.1	0.003	ni	ni	ni	ni	ni	0.01	ni	(FAO/WHO 2019) (FAO/WHO 2021)
FAO / WHO	Leafy vegetable	ni	0.2	ni	ni	ni	ni	ni	0.3	ni	(FAO/WHO 2019) (FAO/WHO 2021)
China	Soil	ni	0.3-0.6	150-300	ni	ni	ni	40-60	80	ni	(Kinuthia et al. 2020) (Antoniadis et al. 2019)
China	Leafy vegetable	0.5	0.2	0.5	ni	ni	ni	ni	0.3	ni	(Kinuthia et al. 2020) (Antoniadis et al. 2019)

* Total Cr. ** Cu dissolved. *** The maximum target for contaminant level considering public health for As and Pb is zero, because neither level is considered safe, however USEPA has set this reference value for monitoring drinking water. **** USEPA recommends secondary standards for potable water systems. Not informed (n.i).

3.1 Trace elements in irrigation water

No detectable levels of As, Cd, Cr, Pb, or Ni were encountered in the irrigation water samples taken from the five community gardens analyzed (Table 3). It is important to note that the concentrations of the other trace elements detected in the irrigation water samples were within environmentally permitted limits (Table 2).

Table 3. Mean concentrations of trace elements detected in irrigation water samples collected in urban gardens in Curitiba City, PR, Brazil, and in the Centro Paranaense de Referência em Agroecologia garden in Pinhas City, PR, Brazil.

Trace elements (mg.mL^-1)
Gardens	Cu	Fe	Mn	Zn
Esquina Verde	0.013ns	0.393ns	nd	0.494ns
Marumbi 1	0.013ns	0.143ns	nd	0.955ns
Marumbi 2	0.019ns	0.215ns	nd	0.763ns
Pantanal	0.020ns	0.224ns	0.010	1.454ns
CPRA	0.020ns	0.147ns	nd	0.646ns

The means were compared using the Tukey Test (p < 0.05). ns = not significant;

nd = not detected.

The irrigation water used in the HEV, HM1, HM2, and HP gardens is fit for human consumption and is supplied by the Paraná Water Company (SANEPAR); the water used for irrigating the HCPRA garden is taken from the Canguiri River in Pinhas, PR, Brazil. Even though they are derived from distinct sources, our results indicate that the irrigation water used in the community gardens studied here do not constitute sources of contamination of the trace elements As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, or Zn.

3.2 Trace elements in the soil (cultivation substrate)

The analyses of the soil samples did not detect any Cd in any of the urban gardens. In general, independent of the specific garden analyzed, the following order of trace element concentrations were identified in the soils: Ni < As < Pb < Cu < Cr < Zn < Mn < Fe (Table 4). The concentrations of all of the trace elements analyzed (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were within the maximum legal environmentally tolerable limits (Table 2).

Table 4. Mean concentrations of the trace elements detected in soil samples collected from urban gardens in Curitiba City, PR, Brazil.

Trace elements (mg.Kg^-1)
Gardens	As**	Cr*	Cu*	Fe	Mn	Ni*	Pb**	Zn*
Esq. Verde	8.35±0.11c	28.52±0.88a	18.03±0.39c	14020.65±163.69cd	100.69±1.14bc	6.83±0.07a	12.34±0.15c	61.92±0.59b
Marumbi 1	9.41±0.31b	25.61±1.85ab	20.73±0.72b	17840.94±899.30ab	140.22±33.54ab	5.00±0.20c	15.49±2.14bc	48.52±3.54bc
Marumbi 2	3.97±0.30e	17.14±0.43b	16.78±0.59c	15854.62±988.82bc	95.62±23.81c	3.87±0.18d	14.42±0.62bc	39.93±6.61c
Pantanal	10.65±0.31a	29.44±1.54a	24.26±1.31a	18845.94±444.60a	344.44±116.91a	8.66±0.62a	15.29±0.68ab	97.28±7.86a
CPRA	5.78±0.00d	29.09±0.00a	23.62±0.00a	8373.71±0.00d	79.97±0.00c	6.36±0.00b	23.80±0.00a	80.90±0.00a

Mean concentrations of trace elements ± standard deviation (SD). * Detection limits using ICP-OES (0.01). ** Detection limits using ICP-OES (0.02). Means followed by the same lowercase letter in any column not significantly differ by the Tukey test (p < 0.05).

The variations of the permitted concentrations of the trace elements will depend on the characteristics of the different soil types. The permitted limits for As are: 75 mg.kg^-1 according to USEPA (2005), 30 mg.kg^-1 according to SEPA China (1995), and 20 mg.kg^-1 according to FAO/WHO (2021), while the permitted limits for Cr, Cu, Fe, Mn, and Zn are similar among almost all of the regulatory bodies of different countries and organizations.

The results of the analyses of the water used for irrigating the urban gardens studied here, as well as their soils, demonstrated that neither constitute sources of trace element contamination in the cultivated plants. The concentrations of trace elements in the HP soil, however, were more elevated (Table 4). That result apparently reflects the location of that garden in a low elevation urban area very near a railyard used for the maintenance, movement, and fueling of locomotives. Galera and Staszewski (Galera and Staszewski 2012) cited train traffic as a source of environmental pollution, especially of heavy metals.

Staszewski et al. (Staszewski et al. 2015) reported trace metal contamination in soils and plants cultivated near train yards in northern Varsóvia, Poland, and toxic levels of As, Mn, and Ni were found in plants growing there (Daucus carota, Pastinaca sativa, Taraxacum officinale, and Sonchus oleraceus). Those authors noted that rail transport is an important source of metal contamination in soils, making it advisable to evaluate the environments surrounding urban gardens to identify potential contamination and pollution problems and to suggest subsidies for their management and control.

3.3 Trace elements in plant biomasses

The trace elements Cd, Ni, and Pb were not detected in any of the L. sativa plants collected in the urban community gardens studied; the concentrations of the trace elements Cr, Cu, Fe, Mn, and Zn are presented in Figures 1A, 1B, 1C, 1D, 1E and 1F respectively. The concentrations of trace elements detected in the studied plants are in accordance with the maximum tolerated limits (Table 2).

Arsenic was only identified in plants grown in the HCPRA garden (Figure 1A), but its concentration was within the limits established by both Brazilian (0.30 mg.kg^-1) and Chinese (0.50 mg.kg^-1) norms (Table 2). The mean concentration of As in L. sativa plants from the HCPRA garden (0.13 mg.kg^-1) was well below the concentration observed in leafy vegetables harvested from conventional agricultural plots (which can reach up to 4.50 mg.kg^-1) (Bati et al. 2017). That observation is related to the pillars of ecological agriculture – no use of industrialized fertilizers and pesticides (which constitute typical sources of As contamination) (Bati et al. 2017).

It is important to note that when As is encountered in leafy vegetables (such as L. sativa), close monitoring of the garden should be undertaken, as species of the Asteraceae family are known accumulators of that metalloid (Ramirez-Andreotta et al. 2013). The tolerable daily consumption of As by humans is only 0.003 mg.kg^-1(WHO 2019). Therefore a 70 kg person should only digest (at most) 0.21 mg of As, which corresponds to ingesting approximately 1.61 kg of lettuce produced in the HCPRA per day, which is much higher than the average consumption of L. sativa in Brazil (0.69 Kg.year^-1) (HFBrasil 2021). Additionally, L. sativa is not the only possible source of As that can enter the human diet, which reinforces the necessity of monitoring production from urban gardens.

The soils of urban gardens must also be considered. Although the As concentration in the HCPRA soil was less than was observed in the other gardens evaluated, it is an organosol rich in organic material that, according to (Kabata-Pendias 2011; Meunier et al. 2011), increases the bio-availability of metalloids. Smith et al. (2002) noted that the bio-availability of As in a given soil is controlled by both adsorption and desorption reactions. Those reactions, and the available concentration of As, are controlled by the physical, chemical, and biological attributes of the soil.

The trace elements As, Cd, Ni, and Pb were not detected in any of the analyses performed on B. oleracea plants grown in the urban gardens studied here; the concentrations of the trace elements Cr, Cu, Fe, Mn, and Zn are presented in Figures 2A, 2B, 2C, 2D and 2F respectively.

Chrome concentrations in samples of L. sativa plants varied from 0.53 to 2.06 mg.kg^-1, and from 0.16 to 1.98 mg.kg^-1 in samples of B. oleracea. The greatest concentrations of Cr in L. sativa plants were observed in the HP and HM1 gardens (Fig. 1A), and were significantly higher than levels seen in the other urban gardens. The greatest concentrations of Cr in B. oleracea plants were observed in the HP, HM1, and HM2 gardens, and were significantly higher than in the other two gardens examined. The levels of Cr in both vegetables were found to be below the safe upper limits set by USEPA and FAO/WHO (2021) of 2.30 mg.kg^-1. The Cr concentrations in L. sativa as encountered here were similar to those reported by De León et al. (2010) in peri-urban areas located in the southern region of Mexico City in a non-protected area and in an area protected (covered by a filtering mech to diminish atmospheric pollution) from atmospheric pollution (2.60 and 1.60 mg.kg ^-1 respectively). The values reported here were, however, greater than those reported by Chang et al. (2014) in L. sativa plants sold in a supermarket (0.13 mg.kg^-1).

In relation to Cr levels in B. oleracea, greater concentrations were observed in Brassica oleracea var. capitataem (0.36 mg.kg^-1) by Bati et al. (2017) and in Brassica rapa subsp. pekinensis (0.36 mg.kg^-1) produced through conventional cultivation (Chang et al. 2014); Bati et al. (2017) did not observe any Cr in samples of B. oleracea plants grown in peri-urban gardens.

In relation to Cu, the concentrations observed in L. sativa varied from 6.69 to 8.92 mg.kg^-1, while the concentrations observed in B. oleracea varied from 2.25 to 5.24 mg.kg^-1. Cu levels of both of the vegetables studied here were found to be below the safe limits set by FAO/WHO (1989) (73.30 mg.kg^-1). França et al. (2017) evaluated the concentrations of Cu in L. sativa plants produced in conventional gardens in peri-urban gardens in Pernambuco State, Brazil, and reported only low Cu concentrations (varying from 3.7 to 5.3 mg.kg^-1). De León et al. (2010) likewise encountered low Cu concentrations in L. sativa plants cultivated in both protected and unprotected gardens in the southern region of Mexico City (3.60 and 5.90 mg.kg ^-1respectively). In relation to Cu concentrations found in B. oleracea plants from the gardens studied here, there values were inferior to those obtained by Bati et al. (2017) from B. oleracea plants grown in conventional gardens (8.06 mg.kg^-1), and by Radulescu et al. (2013) from B. oleracea plants cultivated in urban and peri-urban gardens (14.23 mg.kg^-1).

The concentrations of Fe, Mn, and Zn identified in L. sativa plants grown in the urban garden studied here varied from 101.60 to 218.21 mg.kg^-1, from 11.01 to 26.95 mg.kg^-1, and from 50.32 to 99.28 mg.kg^-1 respectively. Those concentrations were below the concentrations observed in L. sativa samples from a supermarket as evaluated by Nali et al. (2009), which were 560 mg.kg^-1 for Fe, 45 mg.kg^-1 for Mn, and 75 mg.kg^-1 for Zn. In terms of the B. oleracea plants examined in this study, the concentrations of Fe, Mn, and Zn varied from 61.96 to 105.17 mg.kg^-1, from 4.70 to 22.80 mg.kg^-1, and from 24.20 to 59.51 mg.kg^-1 respectively. The levels of Fe and Zn in both vegetables studied were found to be below the safe limits set by WHO (2001, 1995), see Table 5.

The concentrations of Fe reported here for B. oleracea (Figure 2C) were inferior to those observed by Radulescu et al. (2013) for plants raised in urban and peri-urban gardens (206.34 mg.kg^-1). The concentrations of Mn and Zn (Figures 2D and 2E) reported here, however, were greater than those encountered by Harmanescu et al. (2011) in Brassica oleracea var. capitata plants cultivated in an agroecology garden (3.85 mg.kg^-1 of Mn and 59,51 mg.kg^-1 of Zn), in an industrial and mining area (10.47 mg.kg^-1 of Mn and 8.51 mg.kg^-1 of Zn), and in an urban and peri-urban region (9.15 mg.kg^-1 of Mn and 3.28 mg.kg^-1 of Zn).

Our results are within the values and/or limits of the average concentrations of the potentially toxic elements Cr, Cu, Fe, Mn, and Zn reported in the literature (Table 5).

Table 5. Reported values of potentially toxic elements in the edible portions of Lactuca sativa and Brassica oleracea plants (mg.kg-1, dry weight).

Trace elements in Lactuca sativa
City	Local	Cr	Cu	Fe	Mn	Zn	Source
Iwate Prefecture, Japan	Vegetables on the market	4.38	5.38	157	78.2	52.7	(ITOH et al. 2006)
Mexico City, Mexico	Peri-urban area – protect site	2.6	3.6	-	21.7	-	(De León et al. 2010)
Mexico City, Mexico	Peri-urban area – unprotect site	1.6	5.9	-	67.3	-	(De León et al. 2010)
Copenhagen, Denmark	Urban gardening	0.24-0.38	5.99-8.66	-	-	43.30-77.90	(Warming et al. 2015)
Recife, Brazil	Urban garden	0.69-2.27	10.45 -11.62	160.00-170.0 0	20.00	59.00-65.00	(Mancarella et al. 2016)
Marrakech, Morocco	Urban area	1.3	12.9	-	35.2	46.7	(Laaouidi et al. 2020)
São Paulo Region Metropolitan, Brazil	Urban garden	7.0	4.0-6.0	169.0	18.0	38.0	(Sussa et al. 2022)
Curitiba, Brazil	Urban garden	0.53-2.06	6.69-8.92	101.60-218.21	11.01-26.95	50.32-99,28	This research
Trace elements in Brassica oleracea
Zanzibar, Tanzania	Markets	1.80	3.54	176.00	35.80	16.2	(Mohammed and Khamis 2012)
Zanzibar, Tanzania	Farms (production sites)	2.06	10.3	574.2	52.2	26.3	(Mohammed and Khamis 2012)
Copenhagen, Denmark	Urban gardening	0.20-0.24	3.08-5.50	-	-	23.30-66.40	(Warming et al. 2015)
Jhenaidah district, Bangladesh	Sub-urban industrial area	-	-	-	6.1	38.0	(Islam et al. 2018)
Curitiba, Brazil	Urban garden	0.16-1.98	2.25-5.24	61.96-105.17	4.70-22.80	24.20-59.51	This research
Limits values		Edible parts of vegetables
Limits values		2.3^*	40**	-	500*	100**	(WHO 2001) *(WHO 1995)

It is important to note that the consumption of L. sativa and B. oleracea plants cultivated in the urban gardens in Curitiba City can contribute to the daily ingestion of the trace elements Cr, Cu, Fe, Mn, and Zn (Table 6).

Table 6. The concentrations of trace elements supplied by the daily consumption of L. sativa and B. oleracea plants grown in urban gardens, based on the mean annual consumption of 0.69 kg.

Species (source)		Trace elements
Species (source)		Cr	Cu	Fe	Mn	Zn
Lactuca sativa	Daily consumption (mg.kg^-1.d^-1)	0.002	0.014	0.291	0.028	0.118
Lactuca sativa	Dietary contribution (%)	0.71	10.37	10.77	0.11	0.10
Brassica oleracea	Ingestão diária (mg.kg^-1.d^-1)	0.002	0.043	0.005	0.030	0.081
Brassica oleracea	Dietary contribution (%)	0.64	32.35	0.18	0.12	0.07

*The daily ingestion calculation is based on the mean concentrations of trace elements among all of the gardens evaluated.

**Values obtained according to Brasil (2018).

Chrome is an essential element for humans – being required for the metabolism of carbohydrates and lipids (Nali et al. 2009). The consumption of Cr in human diets, however, is often sub-optimal as most diets contain less than 60% of the suggested minimum daily intake of that trace element for adults (0.005 mg.kg^-1) (Nali et al. 2009). Considering that the mean annual consumption of L. sativa and B. oleracea by a 70 kg person is 0.69 kg (HFBrasil 2021) and the mean concentration of Cr in plants produced in the urban gardens analyzed here, the consumption of L. sativa and B. oleracea contribute to the daily ingestion of only 0.002 mg.kg^-1, equivalent to only 0.71% and 0.64%, respectively, of the daily recommended intake of that trace element (Table 6) – although it represents a contribution to the suggested daily consumption well above that provided by L. sativa plants sold in supermarkets (Chang et al. 2014).

The recommended minimum daily consumption of Cu by adults is 0.135 mg (Brasil 2018). The L. sativa and B. oleracea plants cultivated in the urban garden studied here therefore contribute to daily ingestions of 0.014 mg.kg^-1and 0.043 mg.kg^-1 of Cu (approximately 10% and 32% of the recommended minimum daily requirement respectively) (Table 6).

Finally, considering the recommended minimum daily requirement of Fe (2.7 mg), Mn (24.5 mg), and Zn (115.5 mg) by a 70 kg person (BRASIL, 2018), the L. sativa plants grown in the urban gardens studied here can contribute approximately 10%, 0.11%, and 0.10% of those requirements respectively (Table 6). The B. oleracea plants from those gardens can contribute approximately 0.18%, 0.12%, and 0.07% of the recommended daily requirement of Fe, Mn, and Zn respectively (Table 6).

Urban agriculture has become a common practice in developing countries, but the food safety of those products must be constantly monitored to minimize any risks to public health. We analyzed here the quantities of some trace elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) to provide a measure of the food security of vegetables produced in community urban gardens in Curitiba City, PR, Brazil. Food contaminants, especially trace elements, can represent significant health risks, depending on the types of vegetables produced (which demonstrate different accumulation patterns) and the quantities of those chemicals present in the soil and irrigation water. The soils of the community gardens evaluated, and the water used to irrigate them, are in conformity with the maximum recommended limits. In terms of the presence of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, the L. sativa and B. oleracea plants produced in the urban gardens and in the agroecology site were found to be secure for human consumption, as the trace element levels found in the samples were well below the maximum recommended limits.

The expansion of urban gardens is associated with a wide range of benefits, including: food security, healthy diets, recycling of organic residues through composting, as biodiversity refuges, spaces for environmental education activities, and the creation of environments for leisure and social integration. The periodic monitoring of trace elements in edible vegetables is extremely important for the identification of possible sources of pollution (e.g., atmospheric, soil, and irrigation water) and can eliminate or reduce the exposures of plants, animals, and humans to high levels of those contaminants.

Author contributions M.L.B., L.T.M and M.P.G conceptualization. M.L.B.performed the experiments and analyzed the data; M.L.B. L.T.M and M.P.G wrote the original draft; M.P.G was responsible for funding acquisition and project administration; M.L.B., L.T.M and M.P.G writing – review & editing.

The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper

ACKOWLEDGMENTS

This research was financed in part by the the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil) – Finance Code 406190/2018-6. M.P. Gomes received research productivity grants from CNPq.

Alfaro MR, Nascimento CWA, Ugarte OM, Álvarez AM, Accioly AMA, Martín BC, Jiménez TL, Aguilar MG (2017) First national-wide survey of trace elements in Cuban urban agriculture. Agron Sustain Dev 37:1–7. https://doi.org/10.1007/s13593-017-0437-7
Andrade MG de, Melo V de F, Gabardo J, Souza LC de P, Reissmann CB (2009) Metais pesados em solos de área de mineração e metalurgia de chumbo: I - Fitoextração. Rev Bras Ciência do Solo 33:1879–1888. https://doi.org/10.1590/s0100-06832009000600037
Antoniadis V, Shaheen SM, Levizou E, Shahid M, Niazi NK, Vithanage M, Ok YS, Bolan N, Rinklebe J (2019) A critical prospective analysis of the potential toxicity of trace element regulation limits in soils worldwide: Are they protective concerning health risk assessment? - A review. Environ Int 127:819–847. https://doi.org/10.1016/J.ENVINT.2019.03.039
ANVISA (2018) Instrução normativa, N. 28, de 26 de julho de 2018. In: Diário Of. da União
Bati K, Mogobe O, Masamba WRL (2017) Concentrations of Some Trace Elements in Vegetables Sold at Maun Market, Botswana. J Food Res 6:69. https://doi.org/10.5539/jfr.v6n1p69
Branco MC, Alcântara FA De (2011) Hortas Urbanas E Periurbanas Brasil. Hortic Bras 29:421–428
Brasil (2009) Resolução, N. 420, de 28 de dezembro de 2009
Brasil (2011) Resolução N. 430, de 13 de maio de 2011
Brasil (2013) Resolução da Diretoria Colegiada, N. 42, de 29 de agosto de 2013. Dispõe sobre o Regulamento Técnico MERCOSUL sobre Limites Máximos de Contaminantes Inorgânicos em Alimentos A
Brasil (2021) Instrução Normativa, N. 88, de 26 de março de 2021. Estabelece os limites máximos tolerados (LMT) de contaminantes em alimentos. Dispõe sobre o Limites Máximos de Contaminantes Inorgânicos em Alimentos. ANVISA.
Brasil (2018) Instrução normativa, N. 28, de 26 de julho de 2018. Diário Oficial Da União.
Carmo CAF de S do, Araújo WS de, Bernardi AC de C, Saldanha MFC (2000) Métodos de Análises de Tecidos Vegetais Utilizados na Embrapa Solos. Circular técnica N. 6, Embrapa Solos, Rio de Janeiro
Chang CY, Yu HY, Chen JJ, Li FB, Zhang HY, Liu CP (2014) Accumulation of heavy metals in leaf vegetables from agricultural soils and associated potential health risks in the Pearl River Delta , South China. Env Monit Assess 1547–1560. https://doi.org/10.1007/s10661-013-3472-0
Chen R, Zhang P, Li L, Xiao J, Su Z, Xiao T (2014) Analysis of Nutrition of Collard Green Grown in China. J Food Process Technol 05: https://doi.org/10.4172/2157-7110.1000306
Dala-Paula BM, Custódio FB, Knupp E, Palmieri HEL, Silva JB, Glória MBA (2018) Cadmium , copper and lead levels in different cultivars of lettuce and soil from urban agriculture. Environ Pollut 242:383–389. https://doi.org/10.1016/j.envpol.2018.04.101
De León CP, Sommer I, Cram S, Murguía F, Hernandez M, Vanegas C (2010) Metal uptake in a peri-urban Lactuca sativa cultivated area. J Environ Sci Heal Part A 45:111–120. https://doi.org/10.1080/10934520903389275
Demirezen D, Aksoy A (2005) Heavy metal levels in vegetables in turkey are. J Food Qual 29:252–265
Drabek MĆ, Piekut A, Gut K, Grabowski M (2020) Risk of cadmium, lead and zinc exposure from consumption of vegetables produced in areas with mining and smelting past. Sci Rep 10:1–9. https://doi.org/10.1038/s41598-020-60386-8
Emamverdian A, Ding Y, Mokhberdoran F, Xie Y (2015) Plant Defense Response. Sci World J 2015:7–9
FAO/WHO (2021) Food security and nutrition in the world for food security, improved nutrition and affordable healthy diets for all. Italy. p.1-240, Roma
FAO/WHO (2019) General Standard for contaminants and toxins in food and feed. Codex Aliment 1–66
França FCSS, Albuuerque AMA, Almeida AC, Silveira PB, Filho CA, Hazin CA, Honorato E V (2017) Heavy metals deposited in the culture of lettuce (Lactuca sativa L.) by the influence of vehicular traffic in Pernambuco, Brazil. Food Chem 215:171–176. https://doi.org/10.1016/j.foodchem.2016.07.168
Galera H, Staszewski T (2012) Railway Tracks - Habitat Conditions , Contamination , Floristic Settlement - A Review. Environ Nat Resour Res 2:1–11. https://doi.org/10.5539/enrr.v2n1p86
Gupta N, Kumar K, Kumar V, Kumar S, Chadd RP, Kumar A (2019a) Trace elements in soil-vegetables interface : Translocation , bioaccumulation , toxicity and amelioration - A review. Sci Total Environ 651:2927–2942. https://doi.org/10.1016/j.scitotenv.2018.10.047
Gupta N, Kumar K, Kumar V, Kumar S, Chadd RP, Kumar A, Yadav KK, Kumar V, Kumar S, Chadd RP, Kumar A (2019b) Trace elements in soil-vegetables interface: Translocation, bioaccumulation, toxicity and amelioration - A review. Sci Total Environ 651:2927–2942. https://doi.org/10.1016/j.scitotenv.2018.10.047
Hanke D, Biesek MF, Winck BR, Silva RW da (2010) Hortas Urbanas Agroecológicas sob Linhas de Transmissão de Energia e o Fortalecimento de Organizações Sociais na Região Sul do Município de Curitiba-PR. Cad Agroecol 5:1–8
Harmanescu M, Alda LM, Bordean DM, Gergen IG and LG (2011) Heavy metals health risk assessment for population via consumption of vegetales grow in old mining area; a case study: Banat Couty, Romania. chemitry Cent J
HFBrasil (2021) HORTIFRUTI/CEPEA: Quais são as frutas e hortaliças mais consumidas pelos brasileiros?
IDR-PR (2021) Centro de Pesquisa em Agroecologia - CPRA
Islam R, Kumar S, Rahman A, Karmoker J, Ali S, Islam S, Saiful Islam M (2018) Trace metals concentration in vegetables of a sub-urban industrial area of Bangladesh and associated health risk assessment. AIMS Environ Sci 5:130–142. https://doi.org/10.3934/environsci.2018.3.130
Islam S, Kormoker T, Mazumder M, Anika SE, Islam T, Hemy DH, Mimi US, Kabir H, Idris AM (2021) Trace elements concentration in soil and plant within the vicinity of abandoned tanning sites in Bangladesh : an integrated chemometric approach for health risk assessment. Toxin Rev 1–16. https://doi.org/10.1080/15569543.2021.1925919
ITOH J, SAITOH Y, FUTATSUGAWA S, SERA K (2006) ELEMENTAL ANALYSIS OF VEGETABLES ON THE MARKET — Comparison with Wild Plants. Int J PIXE 16:209–219. https://doi.org/10.1142/S0129083506000988
Kabata-Pendias A (2011) Trace elements in soils and plants, 3a edn. CRC Press, Taylor and Francis, p.1-533
Kinuthia GK, Ngure V, Beti D, Lugalia R, Wangila A, Kamau L (2020) Levels of heavy metals in wastewater and soil samples from open drainage channels in Nairobi, Kenya: community health implication. Sci Reports2020 10:1–14. https://doi.org/https://doi.org/10.1038/s41598-020-65359-5
Laaouidi Y, Bahmed A, Naylo A, El Khalil H, Ouvrard S, Schwartz C, Boularbah A (2020) Trace Elements in Soils and Vegetables from Market Gardens of Urban Areas in Marrakech City. Biol Trace Elem Res 195:301–316. https://doi.org/10.1007/s12011-019-01849-6
Langemeyer J, Madrid-lopez C, Mendoza A, Villalba G (2021) Urban agriculture - A necessary pathway towards urban resilience and global sustainability? Landsc Urban Plan 210:1–8
Lima MS de, Gadens LN (2019) The Urban Void as a Potential Space to Urban Agriculture Study in Curitiba - Brazil. XI Semin Int Investig en Urban 1–17. https://doi.org/10.5821/SIIU.6598
Mancarella S, Pennisi G, Gasperi D, Marchetti L, Loges V, Orsini F, Gianquinto G, Vianello G, Antisari L (2016) Antimony accumulation risk in lettuce grown in Brazilian urban gardens. Env Qual 20:35–47. https://doi.org/10.6092/issn.2281-4485/6306
Meunier L, Koch I, Reimer KJ (2011) Effects of organic matter and ageing on the bioaccessibility of arsenic. Environ Pollut 159:2530–2536. https://doi.org/10.1016/j.envpol.2011.06.018
Mohammed NK, Khamis FO (2012) Assessment of heavy metal contamination in vegetables consumed in Zanzibars. Nat Sci 04:588–594. https://doi.org/10.4236/ns.2012.48078
Nali C, Balducci E, Frati L, Paoli L, Loppi S, Lorenzini G (2009) Lettuce plants as bioaccumulators of trace elements in a community of central Italy. Env Monit Assess 149:143–149. https://doi.org/10.1007/s10661-008-0189-6
Oliveira DAM, Gandara FB, Khatounian CA (2021) Tipificação de hortas urbanas comerciais no municipío de Piracicaba-SP e Entraves para sua conversão ao manejo orgânico. Rev Bras Agropecuária Sustentável 11:185–194
Pan XD, Wu PG, Jiang XG (2016) Levels and potential health risk of heavy metals in marketed vegetables in Zhejiang, China. Sci Rep 6:1–7. https://doi.org/10.1038/srep20317
Pinto RSBF, Ramos ARR (2008) Avaliação ambiental de hortas urbanas : o caso da cidade de Braga. XIV Congr da APDR 1–29
PMC (2019) Hortas urbanas ressignificam espaços da cidade e transformam vidas em Curitiba. In: GShow
Radulescu C, Stihi C, Popescu I V, Dulama ID (2013) Heavy metal accumulation and translocation in different parts of Brassica oleracea L. ReserchGate 58:1337–1354
Ramirez-Andreotta MD, Brusseau ML, Artiola JF, Maier RM (2013) A greenhouse and field-based study to determine the accumulation of arsenic in common homegrown vegetables grown in mining-affected soils. Sci Total Environ 443:299–306. https://doi.org/10.1016/j.scitotenv.2012.10.095
Sadzawka A, Grez R, Carrasco A, De La Luz M, Revisión MG (2004) Métodos de análisis de tejidos vegetales. Comisión de Normalización y Acreditación Sociedad chilena de la Cencia del Suelo, Santiago
Šamec D, Urlić B, Salopek-Sondi B (2019) Kale ( Brassica oleracea var. acephala ) as a superfood: Review of the scientific evidence behind the statement. Crit Rev Food Sci Nutr 59:2411–2422. https://doi.org/10.1080/10408398.2018.1454400
SANEPAR (2022) Companhia de Saneamento do Paraná
Savi AC, Hutner Júnior OL, Faria FC, Souza Uhmann IM (2019) Práticas de agricultura urbana: uma análise do cultivo de hortaliças em telhados verdes. Brazilian J Dev 5:20746–20749. https://doi.org/10.34117/bjdv5n10-253
SEPA (1995) Environmental quality standards for soils. State Environmental Protection Administration
Shatilov M V, Razin AF, Ivanova MI (2019) Analysis of the world lettuce market. IOP Conf Ser Earth Environ Sci 395:012053. https://doi.org/10.1088/1755-1315/395/1/012053
Silva OH (1999) Agricultura familiar: diversidade e adaptabilidade. Rev Sociol e Política 161–167
Smith E, Naidu R, Alston AM (2002) Chemistry of Inorganic Arsenic in Soils. J Environ Qual 31:557. https://doi.org/10.2134/jeq2002.5570
SMSAN (2020) Agricultura Urbana
Souza JL (2005) Agricultura Orgânica: tecnologia para produção de alimentos saudáveis. Incaper, V. 2, p. 241, Vitória-ES
Staszewski T, Malawska M, Studnik-wójcikowska B, Galera H, Wilkomirski B (2015) Soil and plants contamination with selected heavy metals in the area of a railway junction. Arch Environ Prot 41:35–42. https://doi.org/10.1515/aep-2015-0005
Sussa F V, Furlan MR, Victorino M, Figueira RCL, Silva PSC (2022) Essential and non-essential elements in lettuce produced on a rooftop urban garden in São Paulo metropolitan region (Brazil) and assessment of human health risks. Pre print. https://doi.org/10.21203/rs.3.rs-1782023/v1
USEPA (2007) Method 3051A – Microwave assisted acid digestion of sediments, sludges and soils. United States Environmental Protection Agency-USEPA, Washington, DC
USEPA (2021) National Recommended Water Quality Criteria - Human Health Criteria Table
USEPA (2005a) Guidance for Developing Ecological Soil Screening Levels. Ecological Soil Screening Levels
USEPA (2005b) Guidance for Developing Ecological Soil Screening Levels. Ecological Soil Screening Levels
Veenhuizen R van (2006) Formulating Effective Policies on Urban Agriculture. Urban Agric Mag 16:1–68
Warming M, Hansen MG, Holm PE, Magid J, Hansen TH, Trapp S (2015) Does intake of trace elements through urban gardening in Copenhagen pose a risk to human health? Environ Pollut 202:17–23. https://doi.org/10.1016/j.envpol.2015.03.011
WHO (2019) Preventing disease through healthy environments exposure to lead: a major public health concern. Department of Public Health and Environment, Genebra
WHO (1995) Codex Alimentarius Committe. Joint FAO/WHO Food Standards Programme, vol 21. Food and Agriculture Organization
WHO (2001) Joint FAO/WHO Food Standard Programme Codex Alimentarius Commission Twenty fourth Session Geneva. CODEX A, Intergovernmental Tfon
Yonegura VB, Silva HM (2021) Urban Agriculture and the transformation of life and landscape in Tatuquara, Curitiba-PR. Confin online - Rev Fr Géographie 754:1–10. https://doi.org/https://doi.org/10.4000/confins.41629

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Trace Elements and Security of Foods Produced in Urban Community Gardens, Curitiba, PR, Brazil

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Abstract

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1. Introduction

2. Material and Methods

2.1 Study areas

2.2 Characteristics of the gardens

2.3 Soil evaluations (culture substrates)

2.3 Evaluation of the irrigation water

2.5 Analyses of plant biomass

3. Results and discussion

3.2 Trace elements in the soil (cultivation substrate)

3.3 Trace elements in plant biomasses

Conclusion

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References

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