Examples of particulate matter include ash from smoke in campfires, dust particles around your house, and smoke coming from car exhaust pipes; in areas close to freeways this is a problem. A study conducted on European women indicated that higher exposure to particulate matter during the initial first weeks of their pregnancy resulted in low birth weight babies [10] This toxin is also considered to be the most dangerous of the three because it can be basically anything small enough to be inhaled. This may also be due to the fact that brain growth begins within the first month of conception.