I have been doing landscaping this past summer and will continue it into the fall. All day I have a constant stream of fumes coming from the equipment I use. Is the constant inhalation of these fumes emitted by the gas powered machines harmful to my physiological or mental state? If so, how are they harmful? And what can I do to minimize my level of risk?
Landscaping engines by and large don't have regulated emissions.
Internal combustion engines emit mechanical energy, sound, carbon dioxide, water & heat.
The additional bad stuff can include unburnt hydrocarbons, carbon monoxide, nitrogen oxides, particulates, etc.
Keep engines serviced and well tuned to minimize pollutants.
See if the equipment mfg. can supply an accessory 3-way catalytic converter & heat guard.
Wear a dust mask with activated charcoal & eye/hearing protection & sun block.
You're wise for considering this. By the time you feel problems many times much damage is already done.
Also contact your local osha dept. for additional risk management info.