Question

If a man is exposed to \(255 \mathrm{mrem} / \mathrm{yr}\) of radiation because of radon and his total exposure is 380 mrem/yr, what percentage of his total exposure is due to radon?

Short answer

67.1% of the total exposure is due to radon.

Step-by-step solution

Identify the Amount of Exposure due to Radon

The amount of radiation exposure due to radon is given as 255 mrem/yr.

Identify the Total Radiation Exposure

The total radiation exposure is given as 380 mrem/yr.

Calculate the Percentage of Total Exposure due to Radon

To find what percentage of the total exposure is due to radon, divide the exposure due to radon by the total exposure and then multiply by 100. The formula is: \( \text{Percentage} = \left( \frac{\text{Exposure due to radon}}{\text{Total exposure}} \right) \times 100 \% \).

Key concepts

Radon Exposure

Radon is a natural radioactive gas that you can't see, taste, or smell. It's released from the decay of uranium found in rocks and soil. When it gets trapped inside buildings, such as homes, schools, or offices, it can reach harmful levels. Being exposed to radon is a health concern because it's the second leading cause of lung cancer after smoking.

Since radon is everywhere, we're all exposed to some level of it. Radon levels are typically measured in picocuries per liter (pCi/L) in the air or in working level months (WLM) for occupational exposures. However, to understand the impact on human health, we often use millirems (mrem), a unit of radiation dose, which allows for easier calculation of radon's contribution to an individual’s overall exposure.

In the original exercise, a man's exposure to radon is 255 mrem/yr. This figure can be compared to the Environmental Protection Agency's (EPA) recommended action level of 4 pCi/L for radon in homes, which they estimate corresponds to about 0.2 rem (200 mrem) of dose per year if you were to be exposed to this level of radon for a year.

Radiation Exposure Percentage

Understanding the percentage of radiation exposure from different sources is critical for both safety and regulatory purposes. The exercise provided asks us to calculate how much of the man's annual radiation dose is attributable to radon.

The concept behind this calculation is relatively straightforward: By dividing the dose from radon by the total radiation dose and multiplying by 100, we convert the fraction into a percentage. This percentage is vital for assessing risk and determining if mitigation measures like improved ventilation or radon remediation need to be put in place.

For the man in the exercise, his radon exposure stands at 255 mrem/year out of a total exposure of 380 mrem/year. Using the provided calculation method, he would find that approximately 67% of his total radiation exposure is due to radon, highlighting the significance of this single source within his environment.

Radiation Units

Radiation dose quantities are a complex topic because there are several units used to measure different aspects of radiation. Some common units include the rad, rem, sievert (Sv), and gray (Gy).

Here's a simplified guide to some of the common units:

• Rad (Radiation Absorbed Dose): This unit measures the amount of radiation energy absorbed in a substance.
• Rem (Roentgen Equivalent Man): This unit is used to measure the biological effects of radiation. It is equivalent to the rad but takes into account the type of radiation and its impact on human tissue.
• Sievert (Sv): The Sievert is essentially the same as the rem, but it's the standard unit used internationally in the Metric system.One Sv is equal to 100 rem.
• Gray (Gy): A gray is similar to a rad but is the international Metric unit for the amount of radiation absorbed by a substance.One Gy is equal to 100 rad.

In the context of the exercise, the unit used is mrem which stands for millirem, or one-thousandth of a rem. These units are crucial for calculating exposure and establishing safety standards to protect from the harmful effects of radiation.