A biohazard is anything deemed to create interference in natural life forms evolution and internal life processes. In medical usage it implies narrowly a bloodborne pathogen. By definition, it implies that some biohazard response is required, to detect threats to biosafety in time to respond and preserve the wild or human life threatened, without increasing the overall risks to such life. The biohazard sign is used to indicate any such hazards, the intent being to minimize the need for response by ensuring that those unprepared to deal with the hazard, don't go near it. A process of biosurety involves response to restore biosafety. Biosafety and biosecurity are goal states, biosurety is a goal assured by the identification of biohazards and directing of responses.
In the broadest definition, anything hazardous to life could be a biohazard, e.g. a vote for Dick Cheney. However, unless there's a biological basis for the claim that involves no ontological distinctions, it would be wrong to call anything a biohazard. Cheney, technically, authorizes the creation of new biohazards, and their use in war, but he does not himself constitute a biohazard - yet.
According to the biohazard response yahoogroup, "Many means of control are necessary. Such means as prior restraint, Precautionary Principle, and avoiding complex protocols of permission impeding action... Measurement of biohazards of all kinds, not merely those defined in the International Biosafety Protocol [but also] bioweapons, nanoweapons, exobiology, anthropic bias, technologies, natural habitat destruction and loss of arable land are all biosafety issues." Detection and actual emergency response issues, and team cohesion in "bloom" response" are, the group claims, "not explicitly addressed in the politically-defined protocol" Hazard definition and enforcement are presently inadequate to deal with a "continuum of biohazard detection and response problems" involved in maintaining:"
- clean flow of O2, N2, CO2, H2O to cells.
- free access of natural plants to UV light
- keeping DNA/RNA replication mutagen free
- keeping cell genesis free of interference from toxins, mutagens, pathogens of all kinds
- keeping animal body organs free of species specific mutations preventing wild survival
- keeping animal bodies fit for wild survival - preventing engineered competitors (e.g. fit as food animals only) from crowding out wild/natural progenitors
- keeping animal societies and habits free of human toxins and mutagens, flooding or desertification due to human practices
Action to ensure any of these is thus, by the group's definition, a biohazard response. Some groups have tried to invent the word ecohazard for this, but this downgrades its importance.