RATIONALE: Mold is not commonly thought of as an outdoor winter allergen in northern climates. This study reports the presence of mold spores in winter months and examines the relationship of climatic variables with outdoor spore levels.METHODS: Mold spores were sampled from air using a Rotorod volumetric sampling device. Spore counts were performed daily, using light microscopy (100X). Each species of mold was reported as the average number of spores per cubic meter of air sampled (spores/m^3/day). These data were obtained between November 1, 2003 and March 31, 2004. Climatic data measured at Newark International Airport was obtained from the National Climatic Data Center. Spearman's correlation coefficients were calculated using SPSS software.RESULTS: Mold spores were identified throughout the winter season. Spore counts reached a season low in December of 118 spores/m^3/day. Alternaria (rho 0.535), Cercospora (rho 0.500), Cladosporium (rho 0.682), Epicoccum (rho 0.633), Smuts (rho 0.575) positively correlated with temperature. Alternaria (rho 0.447), Cercospora (rho 0.475), Cladosporium (rho 0.652), Epicoccum (rho 0.544) positively correlated with dew point. Only Cercospora (rho 0.476) positively correlated with humidity. Cladosporium (rho -0.448), Epicoccum (rho -0.503), Rusts (rho -0.444), Smuts (rho -0.442) negatively correlated with snowfall. All correlations were significant at the 0.05 level (2-tailed).CONCLUSIONS: Outdoor mold is identifiable throughout the coldest months of the New Jersey winter and can be considered a perennial aeroallergen. Most mold species increased with rising atmospheric temperature and dew point. Other mold species decreased with snowfall. RATIONALE: Mold is not commonly thought of as an outdoor winter allergen in northern climates. This study reports the presence of mold spores in winter months and examines the relationship of climatic variables with outdoor spore levels. METHODS: Mold spores were sampled from air using a Rotorod volumetric sampling device. Spore counts were performed daily, using light microscopy (100X). Each species of mold was reported as the average number of spores per cubic meter of air sampled (spores/m^3/day). These data were obtained between November 1, 2003 and March 31, 2004. Climatic data measured at Newark International Airport was obtained from the National Climatic Data Center. Spearman's correlation coefficients were calculated using SPSS software. RESULTS: Mold spores were identified throughout the winter season. Spore counts reached a season low in December of 118 spores/m^3/day. Alternaria (rho 0.535), Cercospora (rho 0.500), Cladosporium (rho 0.682), Epicoccum (rho 0.633), Smuts (rho 0.575) positively correlated with temperature. Alternaria (rho 0.447), Cercospora (rho 0.475), Cladosporium (rho 0.652), Epicoccum (rho 0.544) positively correlated with dew point. Only Cercospora (rho 0.476) positively correlated with humidity. Cladosporium (rho -0.448), Epicoccum (rho -0.503), Rusts (rho -0.444), Smuts (rho -0.442) negatively correlated with snowfall. All correlations were significant at the 0.05 level (2-tailed). CONCLUSIONS: Outdoor mold is identifiable throughout the coldest months of the New Jersey winter and can be considered a perennial aeroallergen. Most mold species increased with rising atmospheric temperature and dew point. Other mold species decreased with snowfall.