The journal Environmental Science and Pollution Research has published a study carried out in Madrid which relates the levels of environmental pollution, levels of grass pollens and their main allergens, with the symptoms of allergic patients to grasses.

This study was carried out over 18 consecutive months, including two pollination periods and an interval outside the pollen season. The relationships between the different parameters considered were analyzed using different statistical techniques, including a categorical principal component analysis (CatPCA).

The study has been carried out with the participation of:

1. Servicio de Alergia, Hospital Los Madroños, Brunete, Madrid, Spain
2. Clínica Subiza, Madrid, Spain
3. Inmunotek S.L., Alcalá de Henares, Madrid, Spain
4. College of Medicine, University of South Florida, Tampa,
   Florida, USA
5. Unidad de Estadística, Secretaría Adjunta de Informática, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
6. Departamento de Ingeniería Química y Ambiental, Universidad
   Politécnica de Cartagena, Cartagena, Spain