Final answer:
The PHAC is committed to disease prevention, control, and public health education, with a focus on environmental health to prevent illness and promote community well-being.
Step-by-step explanation:
The Public Health Agency of Canada (PHAC) focuses on public health education, disease prevention and control, as these are the foundational activities in public health. Environmental health, a critical component of PHAC's work, aims at preventing disease and promoting health through the management of environmental factors. This includes teaching hygienic practices, the deployment of public sanitation systems, and the promotion of immunizations to reduce the risk of disease spillovers in the population. These efforts contribute to positive externalities and public goods by improving overall community health and safety.