Ecotoxicology is the study of the effects of toxic chemicals on biological organisms, especially at the population, community, ecosystem, and biosphere levels. Ecotoxicology is a multidisciplinary field, which integrates toxicology and ecology.
The ultimate goal of ecotoxicology is to reveal and predict the effects of pollution within the context of all other environmental factors. Based on this knowledge the most efficient and effective action to prevent or remediate any detrimental effect can be identified. In those ecosystems that are already affected by pollution, ecotoxicological studies can inform the choice of action to restore ecosystem services, structures, and functions efficiently and effectively.
Ecotoxicology differs from environmental toxicology in that it integrates the effects of stressors across all levels of biological organisation from the molecular to whole communities and ecosystems, whereas environmental toxicology includes toxicity to humans and often focuses upon effects at the organism level and below.
Ecotoxicology is a relatively young discipline that made its debuts in the 1970s in the realm of the environmental sciences. Its methodological aspects, derived from toxicology, are widened to encompass the human environmental field and the biosphere at large. Ecotoxicology emerged after pollution events that occurred after World War II heightened awareness on the impact of toxic chemical and wastewater discharges towards humankind and the environment. The term « Ecotoxicology » was uttered for the first time in 1969 by René Truhaut, a toxicologist, during an environmental conference in Stockholm. As a result, he was de facto recognized as the originator of this discipline. In actual fact, the pioneering role of Jean-Michel Jouany, Truhaut’s assistant, in conceptualising the discipline and in defining its objectives, is now fully recognized. In Jouany’s mindset, ecotoxicology is primarily linked to ecology for its goal seeks to circumscribe the influence that stress factors can have on relationships existing between organisms and their habitat. Jean-Michel Jouany was indeed the young and brilliant mentor of René Truhaut who was at the time empowered to disseminate the emerging discipline proposed by his young assistant at the international level. Jean-Michel Jouany was promoted to the rank of full professor at the University of Nancy in 1969. He then laid out the teaching and research principles for ecotoxicology at the University of Metz with his colleague, Jean-Marie Pelt, as early as 1971. In France, two universities (Metz and Paris-Sud) markedly contributed to expand this burgeoning discipline during the 1980s and 1990s. Several institutes followed suit in this respect. Indeed, CEMAGREF (now IRSTEA), INERIS, IFREMER and CNRS created research units in ecotoxicology, as did other French universities (in Rouen, Bordeaux, Le Havre, Lyon, Lille, Caen…). Fully recognized by institutions, ecotoxicology continues to move forward. While conventional toxicology limits its investigations at the level of organisms, ecotoxicology strives to assess the impact of chemical, physicochemical and biological agents, not only at the individual level, but also at that of populations and entire ecosystems. In this respect, ecotoxicology again takes into consideration dynamic balance under strain. During the 1990s, a new offshoot of ecotoxicology casually appears known as Landscape ecotoxicology, whose objective seeks to take into account interactions between landscape ecological processes and environmental toxicants, in particular for species undergoing impediments linked to migratory passageways* (e.g., salmonids).
Chemicals are shown to prohibit the growth of seed germination of an arrangement of different plant species. Plants are what make up the most vital trophic level of the biomass pyramids, known as the primary producers. Because they are at the bottom of the pyramid, every other organism in an ecosystem relies on the health and abundance of the primary producers in order to survive. If plants are battling problems with diseases relating to exposure to chemicals, other organisms will either die because of starvation or obtain the disease by eating the plants or animals already infected. So ecotoxicology is an ongoing battle that stems from many sources and can affect everything and everyone in an ecosystem 
Total amount of acute toxicity is directly related to the classification of toxicity.
< 1 part per million → Class I
1–10 parts per million → Class II
10–100 parts per million → Class III