What is the difference between positive and negative acceleration?

Takumi works in his yard for 45 minutes each saturday. he works in the morning, and he wears sunscreen and a hat each time he works in the yard. what does takumi hope to reduce through his actions? the likelihood of stochastic effects, such as dna mutations the severity of stochastic effects, such as cancer the severity of non-stochastic effects, such as cancer the likelihood of non-stochastic effects, such as radiation sickness