What chemicals are there?
All living and non-living matter is composed of different combinations of more than 100 elements in the world, such as the two main components of the air we breathe, nitrogen (~80%) and oxygen (~20%), etc. . Simply put, a chemical is an element or a compound formed by a combination of elements.
• Organic chemical include carbon. Organic chemicals are generally present in living organisms (DNA, hormones, proteins, fats) and hundreds of thousands of synthetic organic compounds are produced industrially (eg DDT pesticides, polyvinyl chloride polymers).
• Inorganic chemicals do not contain carbon. There are thousands of natural and synthetic inorganic chemicals (eg borax, chlorine, sulfuric acid) and commonly used metal compounds (eg sodium chloride, table salt).
• Organometallic compounds include metals and carbon (such as tetraethyl lead, once widely used as an octane booster in motor gasoline).
What happens when chemicals are released into the environment?
After chemicals are released into the environment, they undergo natural transformation and transport processes that are influenced by:
• The conditions under which the chemical is released to the environment (e.g. release to air, water or soil;
source and large area source release);
• Environmental conditions (eg temperature of receiving medium, season, amount of sunlight);
• The specific physical and chemical properties of the chemical. As a result of these various factors,
Released chemicals will:
• Distributed in different media (ie air, water, sediment, soil, plants, animals, humans
kind);
• Transformation and degradation into other chemicals.
Finally, as a result of this multi-media action, chemicals and their transformation products will be distributed in the soil
soil, sediment, water, air, plants, animals and humans.
How are chemical risks determined?
To assess the health and environmental risks of chemicals requires an assessment of their physical, chemical and toxicological properties and an estimate of exposure to humans and environmental organisms.
Since the specific characteristics, release conditions and environmental behavior of each substance are unique, systematic assessment of chemicals is required to understand whether they are widely distributed or mainly concentrated in one medium (air, water, sediment, etc.) , soil or biota). Such systematic assessments can determine the nature and extent of local, regional and global impacts of chemicals released to the environment.

Chemical Profile
When assessing the risks posed by a chemical, it is important to consider releases from the widest range, including during manufacture, processing, handling and transport, accidents during manufacture and transport, use of products and articles, product Waste disposal in the manufacturing process and end-of-life stages. This is sometimes referred to as a chemical "life cycle" assessment.