Which of the following is generally true about pest control chemicals?

Pest control chemicals can pose risks to human health due to their toxicological properties. Many pesticides are designed to target specific pests, but they can also affect non-target organisms, including humans, particularly if proper safety measures are not followed. Exposure can occur through various routes such as inhalation, skin contact, or ingestion, especially in cases of improper application or lack of protective equipment. Therefore, it's vital for pest control professionals and consumers to understand the potential hazards associated with these chemicals and to use them safely, ensuring that appropriate safety guidelines and regulations are followed to mitigate risks.

The other choices present misconceptions about pest control chemicals. While some chemicals may have low toxicity to humans and the environment, the statement that all are environmentally safe is inaccurate. Regarding usage, some pesticides may be less effective under certain weather conditions, but there is no absolute rule prohibiting their use during rainy weather. Furthermore, while combining different pest control methods can enhance effectiveness, it is not accurate to say that they are only effective in combination; many chemicals can work effectively on their own when used properly.