Deutsch: Toxizität / Español: Toxicidad / Português: Toxicidade / Français: Toxicitê
Toxicity is the degree to which a substance can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity).

In the environmental context, toxicity refers to the harmful effects of substances on living organisms and ecosystems. It is the degree to which a substance can cause damage or adverse effects when exposed to organisms, including humans, animals, plants, and microorganisms. Toxicity is an important consideration in assessing and managing environmental pollution, chemical exposures, and the overall health of ecosystems. In this answer, we will explore the concept of toxicity in the environment, provide examples of toxic substances, and discuss related concepts and terms.

1. Toxic Substances:
a) Heavy Metals: Heavy metals such as lead, mercury, cadmium, and arsenic are highly toxic to living organisms. They can accumulate in the environment and in the tissues of organisms, leading to long-term health risks.

Example: Mercury pollution from industrial activities can contaminate water bodies, leading to the accumulation of methylmercury in fish and shellfish. Consuming contaminated fish can pose significant health risks to humans, including neurological damage.

b) Pesticides: Pesticides are chemical substances used to control pests in agriculture, forestry, and public health. While they are designed to target specific organisms, many pesticides can have toxic effects on non-target organisms and disrupt ecosystems.

Example: The insecticide DDT, which was widely used in the past, is highly persistent in the environment and can accumulate in the tissues of organisms, causing reproductive and developmental issues in birds and other wildlife.

c) Industrial Chemicals: Various industrial chemicals, such as polychlorinated biphenyls (PCBs), dioxins, and volatile organic compounds (VOCs), can be toxic to both humans and the environment. These substances are often released through industrial processes, waste disposal, and accidents.

Example: PCBs, which were commonly used in electrical equipment, have been found to be persistent, bioaccumulative, and toxic. They can adversely affect the immune system, reproductive system, and neurological development of organisms.

2. Ecological Impacts:
a) Biodiversity Loss: Toxic substances can have severe impacts on biodiversity by directly harming organisms or disrupting ecological processes. They can lead to population declines, species extinctions, and imbalances in food webs.

Example: The use of neonicotinoid insecticides has been linked to the decline of pollinator populations, including bees and butterflies, which are critical for pollination and maintaining ecosystem health.

b) Ecosystem Disruption: Toxic substances can disrupt the functioning of ecosystems by affecting nutrient cycling, energy flow, and the interactions between organisms. This disruption can have cascading effects throughout the ecosystem.

Example: Oil spills in marine environments can have toxic effects on various organisms, including fish, birds, and marine mammals. The contamination of their habitats can result in population declines, habitat degradation, and ecological imbalances.

3. Human Health Impacts:
a) Acute Toxicity: Exposure to highly toxic substances can cause immediate and severe health effects in humans, such as poisoning, organ damage, or even death.

Example: Ingesting or inhaling high levels of certain household cleaning products, such as bleach or ammonia, can lead to acute toxicity symptoms, including respiratory distress, chemical burns, and central nervous system effects.

b) Chronic Toxicity: Chronic exposure to low levels of toxic substances over a long period can have cumulative health effects and increase the risk of chronic diseases, including cancer, neurological disorders, and reproductive issues.

Example: Prolonged exposure to air pollution containing particulate matter, nitrogen dioxide, and volatile organic compounds can contribute to respiratory diseases, cardiovascular problems, and reduced lung function.

Similar concepts and terms related to toxicity in the environmental context include:

- Bioaccumulation: Bioaccumulation refers to the gradual accumulation of a substance in an organism's tissues over time. It occurs when the rate of intake exceeds the organism's ability to eliminate or metabolize the substance.

- Biomagnification: Biomagnification is the process by which the concentration of a substance increases at higher trophic levels in a food chain. It occurs when organisms at lower trophic levels consume contaminated organisms, leading to the accumulation of toxins in higher-level predators.

- Toxicokinetics: Toxicokinetics is the study of how toxic substances are absorbed, distributed, metabolized, and eliminated by organisms. It helps to understand how toxins move through an organism's body and how they are processed.

- Risk Assessment: Risk assessment involves evaluating the potential adverse effects of toxic substances on human health and the environment. It considers factors such as exposure pathways, toxicity data, and the likelihood of exposure.

- Environmental Standards and Regulations: Governments and international organizations establish environmental standards and regulations to limit the release of toxic substances into the environment and protect human health and ecosystems.

In summary, toxicity in the environmental context refers to the harmful effects of substances on living organisms and ecosystems. It encompasses a wide range of toxic substances, ecological impacts, and human health effects. Understanding and mitigating toxicity is essential for safeguarding the environment, protecting biodiversity, and promoting human well-being.