Final answer:
To assess external contamination, comparing pathogen test results of different food samples is effective, while x-ray irradiation is used by USPS and FBI for mail safety. Drugs undergo risk assessments to ensure suitability for human use, and some bacteria serve as indicators of other harmful contaminants.
Step-by-step explanation:
To assess whether a package is externally contaminated, it is essential to look for indicators that may point to the presence of harmful substances. For example, in a lab setting, comparing pathogen test results of food samples can help determine contamination. Another method, used by organizations such as the United States Postal Service (USPS) and the Federal Bureau of Investigation (FBI), involves utilizing x-ray generators to irradiate mail, which can kill bacteria and some viruses, leading to changes in color, texture, and smell as indicators of the process.
In terms of assessing drugs for human use, a robust risk assessment must be conducted to determine its suitability, considering the potential benefits versus risks. Furthermore, certain bacteria are not health threats but are used to indicate the presence of other harmful bacteria, elucidating potential contamination in various scenarios.