Table 3.

Number of research papers per different hazard category and time period, categorized by five UA production contexts and local market assessments.

Hazard category assessed	Period	Soil-based urban and peri-urban greens	Soilless UA systems	Aquaponic plants	Waste assimilating and experimental UA plants	Processing and food industry	Local market survey
Foodborne pathogens and microorganisms	<2001	4	1	0	5	18	3
	2001–2010	5	7	0	5	3	0
	2011–2020	2	29	6	7	24	1
Heavy metals and PTEs	<2001	11	5	1	2	0	5
	2001–2010	14	6	3	3	1	0
	2011–2020	23	9	2	7	2	0
PPP residues	<2001	3	2	0	0	0	0
	2001–2010	2	3	0	0	1	0
	2011–2020	3	5	0	0	2	2
Nitrate and nitrite	<2001	1	3	0	0	1	1
	2001–2010	1	3	0	1	0	0
	2011–2020	1	9	5	0	1	1
Microfauna and pluricellular parasites	<2001	1	0	0	1	1	0
	2001–2010	3	1	0	4	0	0
	2011–2020	0	0	0	0	0	0
POPs	<2001	3	1	0	0	0	0
	2001–2010	2	0	0	0	0	0
	2011–2020	2	2	0	1	0	0
Xenobiotics and pharmaceuticals	<2001	0	0	0	1	0	0
	2001–2010	0	0	0	0	0	0
	2011–2020	2	1	0	1	0	0
Toxins	<2001	0	0	0	0	1	0
	2001–2010	0	0	0	0	0	0
	2011–2020	1	0	0	0	0	0
Hazardous materials	<2001	0	0	0	0	0	0
	2001–2010	0	0	0	0	0	0
	2011–2020	0	0	0	1	0	0

PTEs: Potentially toxic elements: PPP: plant protection products; PoPs: persistent organic pollutants.