When Liberty Quarry proponents tell you that there will be no health effects from the proposed quarry due to silica, dust or other toxic air contaminants, it seems they have missed the Quarrying 101 class.

Our own U.S. Government Occupational Safety and Health Administration website defines crystalline silica as a "basic component" of granite. The website also tells you that the greatest exposure to crystalline silica is from rock drilling and quarry work, among other professions. Further, unlike those who will tell you silica is just like beach sand, respirable crystalline silica is defined as dust not visible to the human eye because of its microscopic size, which "breathing crystalline silica dust can cause silicosis."

In response to the Liberty Quarry draft environmental impact report, the South Coast Air Quality Management District stated: "The lead agency (Riverside County) conducted a localized and regional air quality impacts analysis, the outcome of these analyses demonstrated high levels of emissions resulting in significant impacts from the construction and operation of the proposed project (Liberty Quarry)."

Further, some of the "toxic air contaminates" referenced by the air quality district from the proposed Liberty Quarry project include: hexavalent chromium, diesel exhaust particulate, crystalline silica, arsenic, nickel, benzene, formaldehyde and naphthalene.

The district's response states that: "hexavalent chromium and diesel exhaust particulate comprise 76.8 percent of the total carcinogenic prioritization score." Hexavalent chromium is an ingredient in cement, which is used to produce concrete, and yes, it is planned to have a concrete batch plant at the proposed Liberty Quarry.

Each and every one of us should take the time to research each of the toxic air contaminates referenced, to better understand the potential health impacts of these chemicals.

In the air quality district's comments, it states that it believes that health impacts were underestimated. Further, that nonstandard methodology was used in calculating the impacts, which did not conform to the air quality district's standards, and that those standards would have to be used to obtain an air quality permit.

The district's response also stated: "While the lead agency may allow nonstandard parameters and methodology for air dispersion modeling in the Final EIR, SCAQMD approved parameters and methodology will be required for air dispersion modeling and health risk analysis related to air quality permits."

Finally, the district's response stated: "Because I-15 highway bisects the proposed project and residential receptors, it appears that carcinogenic health risk is underestimated because the incremental increase of diesel truck trips from the proposed project along the I-15 was not included." Those diesel truck trips the responses references include 1,600 truck trips a day, six days a week according to the county's own report.

So I ask you: Who are we to believe? Granite Construction, who will make hundreds of millions of dollars if the project is approved? A consultant who is indirectly paid by Granite to prepare the draft environmental impact report? Or independent governmental agencies whose job it is to protect us?

FRED BARTZ lives in Temecula.