Acknowledgements
The authors are grateful to the nurseries involved in this study
and to Comissão de Coordenação e Desenvolvimento Regional do Norte
(CCDR-N) for kindly providing the outdoor air quality data. The
authors are also grateful to Fundação para a Ciência e a Tecnologia
(FCT), COMPETE, QREN and EU for PTDC/SAU-SAP/121827/2010
funding. SIV Sousa is also grateful to FCT, POPH/QREN and European
Social Fund (ESF) for SFRD/BPD/64686/2009 financial support.