Which statement about vapor drift factors is correct?

• A. Temperature and pesticide volatility are the two most important factors
• B. Temperature is the only factor
• C. Pesticide volatility is irrelevant
• D. Humidity is the only factor that matters

Answer: (A)

Vapor drift is driven mainly by how readily the chemical becomes a vapor and how warm the air is. When the temperature is higher, the pesticide’s vapor pressure increases and more of the chemical can evaporate into the air, making drift more likely. The intrinsic volatility of the pesticide determines how easily it turns into vapor in the first place; a highly volatile compound will contribute more to vapor drift under the same conditions. While humidity and other factors can influence overall drift in some ways, the combination of high temperature and high volatility is the strongest predictor of vapor movement, so stating that these two are the most important factors best captures the key drivers of vapor drift.