Question

The chemical trichloroethylene (TCE) is a colorless liquid found in very low concentration in drinking water. The EPA has set a maximum concentration of TCE in drinking water at \(5 \mathrm{ppb}\). Consuming water on a regular basis that contains higher concentrations can lead to cancer. (a) What is the ppb concentration in a \(200.0-\mathrm{L}\) (200.0 kg) sample of water that contains \(0.43 \mathrm{mg}\) TCE? (b) Is this water safe to drink?

Short answer

The concentration of TCE in the sample is 2.15 ppb, which is less than the EPA's limit of 5 ppb, so the water is safe to drink.

Step-by-step solution

Convert TCE mass into micrograms

First, convert the given mass of TCE into micrograms using the conversion 1 mg = 1000 µg. So, \(0.43 \, \mathrm{mg} * \frac{1000 \, \mathrm{µg}}{\mathrm{mg}} = 430 \, \mathrm{µg}.\)

Calculate concentration in ppb

Next, calculate the concentration using the formula for ppb, which is \( \mathrm{ppb} = (\frac{\mathrm{mass \, in \, µg}}{\mathrm{volume \, in \, L}} ). So, \( \mathrm{ppb} = \frac{430 \, \mathrm{µg}}{200.0 \, \mathrm{L}} = 2.15 \, \mathrm{ppb}.\)

Compare concentration to EPA limit

Lastly, compare your calculated concentration to the EPA's limit. As \(2.15 \, \mathrm{ppb} < 5 \, \mathrm{ppb}\), the water is safe to drink.

Key concepts

Trichloroethylene

Trichloroethylene, often abbreviated as TCE, is a chemical compound that appears as a colorless liquid. Its primary use is as an industrial solvent; it is effective for degreasing metal parts and is also found in some consumer products. Over time, TCE has been found in the environment, often leaching into groundwater, which poses potential health risks. Understanding TCE is important because exposure to this compound can have serious health effects. When present in drinking water, even at low concentrations, it can cause cancer with prolonged exposure. Since it is colorless and often found at low concentrations, TCE can be difficult to detect without proper testing methods.
This is why monitoring drinking water for TCE is crucial, and why it has regulated limits for concentrations, such as the one set by the EPA.

Drinking Water Safety

Ensuring the safety of drinking water is essential for public health. Water can become contaminated with chemicals like trichloroethylene through industrial processes, improperly disposed of waste, or natural groundwater movements. Continuous exposure to contaminated water can lead to a variety of health problems, some of which may not immediately appear. To maintain drinking water safety, water quality is regularly tested for various contaminants. If any chemical in drinking water exceeds the safe consumption limits, actions are taken to rectify the situation. For TCE, proper filtration and remediation techniques can help to reduce its concentration in drinking water.
The goal is to make sure that everyone has access to clean, potable water free from harmful substances, thereby avoiding health risks associated with chemical contaminants.

EPA Regulations

The Environmental Protection Agency (EPA) plays a crucial role in setting safety standards for contaminants in drinking water, including trichloroethylene. The EPA sets a maximum allowable concentration of TCE in drinking water at 5 parts per billion (ppb). This regulation is based on scientific research aimed at minimizing health risks, considering both short-term and chronic exposure levels. EPA regulations help ensure water is safe to consume, protecting consumers from potential health risks associated with contaminated water. By setting these limits, the EPA guides local water authorities in maintaining water quality within safe parameters. Compliance with these regulations is monitored through regular testing and reporting.
If a water supply exceeds the allowable limit, the responsible authorities must take immediate remedial action to cut down the concentrations to acceptable levels, ensuring public health safety.