A 2.6-L sample of water contains \(192 \mu \mathrm{g}\) of lead. Does this concentration of lead exceed the safety limit of \(0.050 \mathrm{ppm}\) of lead per liter of drinking water? [Hint: \(1 \mu \mathrm{g}=1 \times 10^{-6} \mathrm{~g}\). Parts per million (ppm) is defined as (mass of component/mass of so\(\left.\) lution \() \times 10^{6} .\right]\)

The term 'parts per million', or ppm, is a unit of measurement used to describe the concentration of one substance within another. It's a way to express very dilute concentrations of substances. When we say '1 ppm', we mean that there is one part of a substance for every one million parts of the total mixture.

For example, when calculating ppm for a chemical in water, it indicates how many grams of that chemical are present per one million grams of water. To make this more tangible, since the density of water is 1 gram per milliliter, one ppm is also equivalent to one milligram of a substance in one liter of water. This unit is especially useful for measuring very small levels of contaminants, such as lead, in water to assess if they fall within safety guidelines.

Health Implications of Lead

Lead contamination is a serious issue that can have harmful effects on human health. Even at low levels, lead exposure can cause developmental problems in children, including learning disabilities and behavioural issues. In adults, it can lead to high blood pressure and kidney damage among other health concerns.

Identifying Contamination Levels

Identifying the presence of lead in water involves measuring its concentration and comparing it to established safety limits. The process typically requires collecting a water sample and analyzing the amount of lead per volume. Once the concentration of lead is determined, usually expressed in ppm, it can be assessed against safety criteria to decide whether the water is safe for consumption.

The 'water safety limit' for lead, or any contaminant in water, is the maximum concentration considered safe for human consumption. These limits are determined based on scientific research into the health effects of these substances.

The United States Environmental Protection Agency (EPA) has set the action level for lead in drinking water at 0.015 mg/L, which is equal to 0.015 ppm. This metric helps ensure that water providers take necessary actions to control lead levels in drinking water. When calculating ppm concentrations, it is crucial to compare the results to these safety limits to determine if the water quality is acceptable or if it poses a risk to health, prompting the need for treatment or alternate water sources.