Air quality particulate matter guidance, NYC, Oct 2001

NYC 9/11 Public Portal Document

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pH Guidelines

The pH of a substance represents the hydrogen ion concentration of the substance. The range of pH values is generally from 0 to 14 with 7 being considered a neutral pH. Substances with a pH of less than 7 are considered to be acidic and will yield hydrogen ions when they are in solution. Acids will change litmus paper red. A base is a substance with a pH greater than 7 and will yield hydroxyl ions in solution. Bases will react with acids to form salts and water. In the body, a normal balance between acids and bases is maintained that keeps the extracellular fluids in the body with a pH between 7.35 and 7.45. A pH out of this range indicates a state of acidosis or alkalosis. Regulation of the pH in the body depends on the function of the lungs and the kidneys.

Guidelines for the interpretation of the pH values of the dust samples being proposed are included in this plan to assist in defining what role if any that the pH may be in the irritant properties of the dust. An irritant effect is one where the tissue has been stimulated and responds with a reversible inflammatory response. Common symptoms from exposure to an irritant are cough, burning of eyes, nose, & throat, tearing, dyspnea, and wheezing.

There are very few standards for the regulation of the pH of a substance. The national Secondary Drinking water standards set the pH range at 6.5 - 8.5. EPA has established guidelines for the testing of the acute dermal irritation and the acute eye irritation properties of substances. Those guidelines state that it is not necessary to test substances with a pH of less than 2.0 or greater than 11.5 as they are known to be corrosive. A corrosive is a highly reactive substance that causes irreversible damage to living tissue after less than 4 hours of exposure. Using this information as a basis, the following guide is proposed;

pH Acid/base Properties 0-2.0 Strongly acidic Corrosive >2.0 - 6.5 Weakly acidic Irritant >6.5 - 8.5 Neutral >8.5 - 11.5 Weakly basic Irritant >11.5 Strongly basic Corrosive

To put these levels into perspective, the pH of some common substances is included below.

Substance pH Gastric Juice 1.4 Lemon Juice 2.4 Vinegar 3.0 Tomatoes 4.2 Rain 5.5

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