Toxicology is the scientific study of adverse effects that occur in living organisms due to chemicals. It involves observing and reporting symptoms, mechanisms, detection and treatments of toxic substances, in particular relation to the poisoning of humans.
It is difficult to discuss toxic phenomena at different levels of biological organisation separately because of complex relationship and interlinking between such levels. It should be noted that every biological level toxicology includes chemical and/or molecular toxicology in a sense.

Scientists need to study natural situations to understand life processes and to investigate how introducing a particular substance can change living systems. It is often helpful to break a process into steps and then investigate how introduction of the substance affects each step. This first stage in toxicity assessment takes place in vitro. The investigator can pinpoint the various changes that could occur when a compound encounters a living cell and then make safety recommendations. Only a few substances successfully pass these initial trials. Those substances must then be tested further. Humans and other living things—plants, animals, and even molds and bacteria—are complex systems. The processes in any organism are far more complicated than just the sum of the individual parts. It is difficult to replicate at the lab bench the complex interactions. When safety is not assured, ethical research procedures restrict testing on humans. Additional experiments must be performed using other animals first, with the vast majority of animals now used being rats and mice. This is meant to avoid possible toxicity to humans as a result of chemical and molecular changes that occur in some organs and cause harm to other organs, systems and population at large.

Chemicals and/or molecules and biological organs, biological systems and population.

All organisms are composed of chemicals, and chemical reactions power all life processes. When a substance is introduced into an animal, it can interact in many places throughout the whole body, and effects upon one process can cause unexpected consequences in others. Using animals in experiments is critical because such complexity cannot be duplicated in cell culture or in nonliving systems. For example, toxicity can be influenced by the speed with which the substance enters the system, how the liver and other organs change it and how it is taken up by and interacts with various body tissues. Some of the response is influenced by the tissue characteristics (e.g., liver is different than kidney tissue). Because "the dose makes the poison" at the level of the individual organ, we need to be able to analyze not only how a chemical acts, but the relationship between the dose given to the animal and the dose delivered to the different organs and tissues in the body. Studies in whole animals are required to ensure the proper use of beneficial chemicals such as medicines, because the tissue or organ receiving the beneficial effect might be harmed if exposures are greater than needed. In many cases, laboratory tools simply cannot duplicate these complicated phenomena. Ultimately, animal testing is the best method to detect effects such as cancer and birth defects.

It includes environmental agents and chemical compounds found in nature, as well as pharmaceutical compounds that are synthesized for medical use by humans. These substances may produce toxic effects in living organisms including disturbance in growth patterns, discomfort, disease and death.(www.newsmedical.net)

Toxicology research covers toxic phenomena at all levels of biological organisation that is;
• Toxic phenomena at chemical level
• Toxic phenomena at molecular level
• Toxic phenomena at organ level
• Toxic phenomena at biological systems level
• Toxic phenomena at organism level and;
• Toxic phenomena at population level
Chemical Toxicology
Chemical toxicology is a subspecialty of toxicology that focuses on the structure of chemical agents and how it affects their mechanism of action on living organisms.
It is a multidisciplinary field that includes computational and synthetic chemistry, in addition to people who specialize in the fields of proteomics, metabolomics, drug discovery, drug metabolism, bioinformatics, analytical chemistry, biological chemistry and molecular epidemiology. It relies on technological advances to help understand the chemical components of toxicology more comprehensively.(www.newsmedical.net)
Toxicology and Pharmacology Differences
Toxicology and pharmacology are both studies that involve an understanding of chemical properties and their actions on the body, but differ considerably in other areas.
Pharmacology primarily focuses on the therapeutic effects of pharmaceutical substances and how they can be used most effectively for medical purpose. On the contrary, toxicology is more closely related to the adverse effects that can occur in living organisms that come into contact with chemicals. Toxicologists are also more concerned with measuring the risk of certain substances with risk assessment tools.(www.newsmedical.net)
What is Medical Toxicology?
Medical Toxicology is a medical subspecialty focusing on the diagnosis, management and prevention of poisoning and other adverse health effects due to medications, occupational and environmental toxins, and biological agents. Medical Toxicology is officially recognized as a medical subspecialty by the American Board of Medical Specialties.(American College of Medical Toxicologists)
What are some examples of problems evaluated by Medical Toxicologists?
Medical toxicologists are involved in the comprehensive high level care of people and patients who come into contact with drugs, substances or other agents that pose a threat to their well being. The following is a brief list of some of these encounters.
• Unintentional and intentional overdoses of such agents as: o Therapeutic drugs including antidepressants (e.g. tricyclics, serotonin reuptake inhibitors, etc), cardiac medications (e.g. beta-adrenergic blocking agents, calcium channel antagonists, cardioactive steroids such as digoxin, etc.), and many others o Over-the-counter medicines such as aspirin, acetaminophen, ibuprofen, vitamins (e.g. iron supplements, vitamin A, etc.), and more o Drugs of abuse such as cocaine, amphetamines, opioids, cannabis, etc., along with new and emerging agents of abuse such as Salvia Divinorum, ketamine and much more
• Exposure to industrial chemical products and environmental hazards such as: o Pesticides o Heavy metals (e.g. lead, arsenic, mercury) o Household products (e.g. cleaning agents) o Toxic gases (e.g. carbon monoxide, hydrogen sulfide, hydrogen cyanide) o Toxic alcohols (e.g. methanol, ethylene glycol) and other solvents o Other industrial and environmental agents, including radiation exposures
• Drug abuse management including: o Inpatient care for acute withdrawal states from addictive agents such as alcohol and benzodiazepines o Outpatient Medical Review Officer services for industry and organization
• Diagnosis and management of exposures such as: o Envenomations, such as snake bites, spider bites, scorpion stings o Marine toxins such as ciguatera poisoning, paralytic shellfish poisoning, tetrodotoxin and many others o Ingestion of food-borne toxins, such as botulism, scombroid poisoning and more o Ingestion of toxic plants such as thevetia peruviana (i.e. yellow oleander) and mushrooms such as amanita phalloides (i.e. The Death Cap) and gyrometra esculenta (i.e. the false morel)
Independent medical examinations, assessing injury or disability resulting from toxic exposures.(American College of Medical Toxicologists)

REFERENCES.
American College of Medical Toxicologists

www.newsmedical.net