Table 1.

Characteristics of the studied universities.

Monitored Sites	Description
University A	Located in a suburban area
	Surrounded by residences and industries
	Use of a blackboard and chalk
	Built in the 70s
	Presence of vegetation nearby
University B	Located in a suburban area
	Surrounded by residences and buildings
	Use of a blackboard and chalk
	Built in 2000
	No presence of vegetation nearby
University C	Located in a suburban area
	Surrounded by residences and buildings
	Use of blackboard with chalk
	Built in the 70s
	No presence of vegetation nearby
University D	Located in a central area
	Surrounded by residences and buildings
	Use of a blackboard and chalk
	Built in the 70s
	Presence of vegetation nearby
University E	Located in a suburban area
	Surrounded by residences and buildings
	Use of a blackboard and chalk
	Built in the 90s
	No presence of vegetation nearby