Size-fractionated PM10 monitoring in relation to the contribution of endotoxins in different polluted areas

Particulate pollution is an environmental concern that is widespread and difficult to resolve. Recently various regulatory improvements around the world have been agreed upon to tackle this problem, especially as related to the fine fraction of particulates, which more closely correlates to human health effects than other fractions. The size-fractionation of inhalable particles and their organic composition represent a new area of research that has been poorly explored thus far. Endotoxins are a type of natural organic compound that can be found in particulate matter. They are correlated with Gram-negative bacterial contamination. Health outcomes associated with exposure to these toxins are not specific and often overlap with the health effects of PM (Particulate Matter) exposure, including asthma, bronchitis, acute respiratory distress syndrome and organic dust toxic syndrome. Very little information is available on the endotoxin distribution in different PM10 size fractions. This study examined PM10 size fractions and their endotoxin content. Sampling was conducted at five different locations: one urban, two rural and two rural sites that were highly influenced by large-scale farm animal production facilities. For each location, six different PM10 fractions were evaluated. PM10 sub-fractions were categorised as follows: PM10-7.2 (1.15-31.30 µg/m3); PM7.2-3.0 (1.86-30.73 µg/m3); PM3.0-1.5 (1.74-13.90 µg/m3); PM1.5-0.95 (0.24-10.57 µg/m3); PM0.95-0.49 (1.22-14.33 µg/m3) and PM<0.49 (13.15-85.49 µg/m3). The ranges of endotoxin levels determined were: PM10-7.2 (0.051-5.401 endotoxin units (EU)/m3); PM7.2-3.0 (0.123-7.801 EU/m3); PM3.0-1.5 (0.057-1.635 EU/m3); PM1.5-0.95 (0.040-2.477 EU/m3); PM0.95-0.49 (0.007-3.159 EU/m3) and PM<0.49 (0.039-3.975 EU/m3). Our results indicated consistency of the PM1 fraction at all of the sites and the predominant presence of endotoxins in the coarse fraction. The observed abatement of the PM10 and endotoxin levels was very high (above 1:10) as little as 50 meters from the pollution source. This kind of model is useful to both improve our knowledge about PM10 endotoxin distribution and to evaluate the potential risks for the health of neighbouring populations.