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Monday, September 25, 2023

National language

From Wikipedia, the free encyclopedia

A national language is a language (or language variant, e.g. dialect) that has some connection—de facto or de jure—with a nation. There is little consistency in the use of this term. One or more languages spoken as first languages in the territory of a country may be referred to informally or designated in legislation as national languages of the country. National languages are mentioned in over 150 world constitutions.

C.M.B. Brann, with particular reference to India, suggests that there are "four quite distinctive meanings" for national language in a polity:

  • "Territorial language" (chthonolect, sometimes known as chtonolect) of a particular people
  • "Regional language" (choralect)
  • "Language-in-common or community language" (demolect) used throughout a country
  • "Central language" (politolect) used by government and perhaps having a symbolic value.

The last is usually given the title of official language. In some cases (e.g., the Philippines), several languages are designated as official and a national language is separately designated.

Official versus national languages

"National language" and "official language" are best understood as two concepts or legal categories with ranges of meaning that may coincide, or may be intentionally separate. Stateless nations are not in the position to legislate an official language, but their languages may be sufficiently distinct and well-preserved to be national languages. Some languages may be recognized popularly as "national languages," while others may enjoy official recognition in use or promotion.

In many African countries, some or all indigenous African languages are officially used, promoted, or expressly allowed to be promoted (usually taught in schools and written in important publications) as semi-official languages whether by long-term legislation or short-term, case-by-case executive (government) measures. To be official, spoken and written languages may enjoy government or federalised use, major tax-funded promotion or at least full tolerance as to their teaching and employers' recognition in public education, standing on equal footing with the official language(s). Further, they may enjoy recognition as a language used in compulsory schooling and treasury money may be spent to teach or encourage adults in learning a language which is a minority language in a particular area to restore its understanding and spread its moral stories, rhymes, poems, phrases, songs, and other literary heritage which will promote social cohesion (where other languages remain) or will promote nationalist differentiation where another, non-indigenous language is deprecated.

National languages

Albania

Albanian is the national language of Albania. Greek is the national language of the Greek communities, predominately in the south. Aromanian serves as a national language of the Aromanian linguistic minority. Albanian is also the national language of Kosovo, parts of southern Italy, southern Montenegro and southern Serbia. It is a co-official but not a national language of North Macedonia.

Algeria

Arabic is the national language in Algeria. Berber is also an official language. French has no official status but is widely used in education, business and the media.

Andorra

Andorra's national language is Catalan; moreover Catalan is an official language in several territories in Spain (Catalonia, Valencian Community, Balearic Islands), and is spoken (without official recognition or status) in territories in Spain (the Catalan-Aragonese borderlands known as La Franja and the Murcian municipality of El Carche), France (Pyrénées Orientales) and in Italy (Alghero).

Armenia

Armenian language is a separate branch in the linguistic family of Indo-European languages. Armenian is widely spoken in Armenia as well as in its diaspora.

Australia

Australia has no official language, but is largely monolingual with English being the de facto national language. A considerable proportion of first and second generation migrants are bilingual. According to Ethnologue, 81% of people spoke English at home, including L2 speakers. Other languages spoken at home included Chinese 2.9%, Italian 1.2%, Arabic 1.1%, Greek 1%, Vietnamese 0.9% and Spanish 0.4%.

There were almost 400 languages spoken by Indigenous Australians prior to the arrival of Europeans. Only about 70 of these languages have survived and all but 30 of these are now endangered.

Azerbaijan

Azerbaijani language is the national language in Azerbaijan.

Bangladesh

Bengali, the sole official language of Bangladesh, is also the de jure and de facto national language of the country. Establishing Bengali as a national language was one of the key reason for the independence of Bangladesh.

Bosnia and Herzegovina

Bosnia and Herzegovina de jure has three national languages - Bosnian, Croatian and Serbian - which are de facto varieties of one language, Serbo-Croatian. It is officially defined under the three names, corresponding to the country's constituent nations. The Latin and Cyrillic alphabets both have official and equal status.

Bulgaria

Bulgarian is the sole official language in Bulgaria.

Canada

Canada's official languages since the Official Languages Act of 1969 are English (Canadian English) and French (Canadian French). Depending on one's views of what constitutes a "nation", these two languages may be considered two equal national languages of the nation of Canada, or the national languages of two nations within one state, English Canada and French Canada.

Quebec nationalists consider Quebec French the language of the Quebec nation and is that province's official language (and recognized minority in Ontario, Manitoba and Newfoundland and Labrador). Acadian French, the national language of Acadians, is an official language of New Brunswick (and recognized minority in Quebec, Nova Scotia and Prince Edward Island). Newfoundland English dialects differ substantially from other Canadian English ones.

English and French are official in Canada's three territories; two legislate a variety of Indigenous languages in addition. Nunavut and the Northwest Territories (N.W.T.) have as official languages Inuktitut and Inuinnaqtun, with N.W.T. also have a further seven more (totalling eleven official languages): Cree, Dënesųłiné, Gwich’in, Inuvialuktun, North and South Slavey and Tłı̨chǫ. As these official languages are legislated at a territorial (sub-federal) level, they can be construed as national languages.

Besides these there many Indigenous languages of Canada, which are the national languages of one or more First Nations, Inuit or Métis peoples; a number of First Nations and Inuit homelands at the Indigenous government level legislate their language as an official language of the Nation, such as the Nisg̱a’a language by Nisg̱a’a and Inuvialuktun by Inuvialuit. Notably the Cree language is spoken (with variations) from Alberta to Labrador, Anishinaabemowin is spoken across central Canada, and Inuktitut is spoken across the Arctic, northern Quebec and Labrador.

China

There are many languages spoken across China, with most people speaking one of several varieties of Chinese. During successive imperial dynasties, the spoken language of the capital city served as the official spoken language and was used across the country by government officials who traveled to communicate with one another. Dialects used for this purpose in different eras included those of Xi'an, Luoyang, Nanjing, Beijing, and other historical capital cities.

After the Xinhai Revolution in 1911, the Kuomintang (Chinese nationalists) founded the Republic of China. In order to promote a sense of national unity and enhance the efficiency of communications within the nation, the government decided to designate a national language. The Beijing dialect of Mandarin and Guangzhou dialect of Cantonese were each proposed as the basis for a national language for China. In the beginning, there were attempts to introduce elements from other Chinese varieties into the national language in addition to those from the Beijing dialect; this was reflected in the first official dictionary of the national language, given the name 國語 (Pinyin: Guóyǔ, literally "national language"). But this artificial language had no native speakers and was difficult to learn, so it was abandoned in 1924. Ultimately, the Beijing dialect was chosen as the national language and it continued to be referred to as 國語 in Chinese in the Republic of China. Since then, the Beijing dialect has become the main standard for pronunciation, due to its prestigious status during the preceding Qing dynasty.

Still, elements from other dialects do exist in the standard language, which is now defined as reflecting the pronunciation of Beijing, the grammatical patterns of Mandarin dialects spoken in the northern parts of China, and the vocabulary of modern vernacular Chinese literature. The People's Republic of China renamed the national language 普通话 (Pinyin: Pǔtōnghuà, literally "common speech"), without otherwise changing the definition of the standard national language.

Croatia

The Croatian language is the official language of Croatia. "The Croatian language and the Latin script shall be in official use in the Republic of Croatia" in Article 12 of the Croatian Constitution.

Czech Republic

The Czech language is the national language of the Czech Republic.

Ethiopia

Amharic was the national language in Ethiopian Empire. The country is composed of at least 80 different ethnic nationalities. Its people altogether speak over 80 different languages. Amharic, Oromo, Tigrinya, Somali, and Afar are the official working languages of Ethiopia. But courts, and legislations work in Amharic and the constitution of the country is written in Amharic in an official capacity. And in day-to-day basis, Amharic is used to issue driving licenses and report tax income, making it not a national language but official language of the government.

Finland

Finland has two national languages: the Finnish language and the Swedish language. The Constitution of Finland guarantees the right to use Finnish and Swedish in courts and other state institutions. Despite the large difference in the numbers of users, Swedish is not officially classified as a minority language but equal to Finnish. Both national languages are compulsory subjects in school (except for children with a third language as mother tongue) and a language test is a prerequisite for governmental offices where a university degree is required. The constitution also grants the Sami and the Roma peoples the right to maintain and develop their languages: The Sami have partial right to use Sami languages in official situations according to other laws.

France

French is the sole official language of France, according to Article 2 of the French Republic's constitution.

Germany

The official language of Germany is German, with over 95% of the country's population speaking it as their first language.

Haiti

Haiti's official languages are Haitian Creole and French. While French is the language used in the media, government and education, 90–95% of the country speak Haitian Creole as the home language while French is learned in school.

Iceland

Icelandic is the official language of Iceland. Icelandic is the language used in the media, government and education, 98% of the country speak Icelandic at home.

India

There is no national language for India as there are more than 780 languages and more than 19,000 dialects in India.

The Union government uses Hindi and English as official languages, such as for parliamentary proceedings and texts of national laws. Communications between the union government and state governments are in Hindi with Region A and Region B states and in English with Region C states. State governments use their own native languages in official communications. They may adopt one or more of the 22 languages listed in the Indian constitution's eighth scheduleAssamese, Bengali, Bodo, Dogri, Gujarati, Hindi, Kannada, Kashmiri, Konkani, Maithili, Malayalam, Marathi, Meitei, Nepali, Odia, Punjabi, Sanskrit, Santali, Sindhi, Tamil, Telugu and Urdu. The Indian supreme court uses English as its sole official language; high courts in some states use other languages spoken in the state in addition to English.

Indonesia

The official and national language of Indonesia is Indonesian. Indonesia has more than 700 living languages, making it the second most linguistically diverse country after Papua New Guinea. These 700+ languages, however, are without official status, and some are in danger of extinction. The largest local language is Javanese.

Iran

Persian (or Farsi) is recognised as the national language of Iran.

Ireland

Irish is recognised by the Constitution of Ireland as the national language and first official language of Ireland, and the English language is recognised as a second official language.

Israel

Hebrew became the national language and the sole official language of Israel with the adoption of the Nation-State Bill in 2018, and Arabic was abolished as a co-official language and became recognized as a language with "special status" used in state institutions.

Italy

The Italian language is the de jure and de facto official language of Italy. Italian is also referred to as national language for historical and cultural reasons, because since the 15th century, Italian became the language used in the courts of nearly every state in Italy and in general among educated Italians (scholars, writers, poets, philosophers, scientists, composers and artists) who contributed to what is nowadays the culture of Italy. Furthermore, Italian was often an official language of the various Italian states before unification, slowly replacing Latin, even when ruled by foreign powers (such as the Spaniards in the Kingdom of Naples, or the Austrians in the Kingdom of Lombardy–Venetia).

Kenya

While English and Swahili are official languages, Swahili also has a special status as national language. None of the country's biggest languages (Gikuyu, Luo, Kamba, Kalenjin, etc.) have any explicit legal status on the national level, but the 2010 constitution enjoins the state to "promote and protect the diversity of language of the people of Kenya."

Lebanon

In Lebanon, the Arabic language is the "official national" language. Modern Standard Arabic is used for official purposes, while the everyday spoken language is Lebanese Arabic. French and English are also widespread in Lebanon.

Luxembourg

Luxembourg uses three official languages: Luxembourgish, French, and German. Previously Luxembourgish had no official status, but following a constitutional revision a law was passed on 24 February 1984 making Luxembourgish the national language. Furthermore, this law recognised the three languages of Luxembourg (Luxembourgish, French and German) as administrative languages.

Malaysia

The Malay language is the national language of Malaysia in accordance with Article 152(1) of the Federal Constitution of Malaysia.

Maldives

Dhivehi is the national language of Maldives per the Maldivian constitution.

Malta

The Maltese language is the national language of Malta. It is also the official language of the island, together with English. Maltese only is recognised as "national" in Chapter 1 of the Laws of Malta.

Namibia

Although English is the only nationwide official language in Namibia, there are also 20 national languages, which are each spoken by more or less sizeable portions of the population and are considered Namibia's cultural heritage. All national languages have the rights of a minority language and may even serve as a lingua franca in certain regions. Among Namibia's national languages are German, Afrikaans, Oshiwambo, Otjiherero, Portuguese, as well as the languages of the Himba, Nama, San, Kavango and Damara.

Nepal

Nepali is the official language in the federal government of Nepal. Over 123 languages are spoken in Nepal, all of which are granted constitutional status as rāṣṭrabhāṣā (राष्ट्रभाषा), officially translated as 'languages of the nation' (the word rāṣṭrabhāṣā also simply means 'national language'). Some of the languages include: Nepal Bhasa, Tamang, Sherpa, Rai, Magar, Gurung, Maithili, Awadhi, English, Limbu, Bhojpuri, etc.

The Netherlands

Dutch is the official language of The Netherlands. In the province of Fryslân they speak Frisian, which is recognized as the second official language there.

New Zealand

While the population of New Zealand is predominantly English-speaking, the language of the indigenous Polynesian people is the Māori language. Both these languages have official status in the country, along with New Zealand Sign Language, which is one of the few sign languages in the world to have such status.

Nigeria

Besides official English (Nigerian Standard English), Nigeria recognizes three 'majority', or national, languages. These are Hausa, Igbo, and Yoruba, each with some 20 million speakers or more.

Pakistan

Article 251(1) of the 1973 Constitution of Pakistan, titled National language, specifies: "The National language of Pakistan is Urdu, and arrangements shall be made for its being used for official and other purposes within fifteen years from the commencing day." Although Urdu has been declared an official language, so far all government documents, legislation, legal orders, and other official records are written in Pakistani English. Most higher education instruction is in English. The National Language Authority is an organization established to make arrangements to promote Urdu since 1979.

Philippines

Filipino is the national language of the Philippines. The current 1987 constitution designated the Filipino language, which is based on Tagalog with the inclusion of terms from all recognized languages of the Philippines, as the national language. It also designated both Filipino and English as the official languages for purposes of communication and instruction, and designated the regional languages as auxiliary official languages in the regions to serve as auxiliary media of instruction therein.

More than 170 languages are spoken in the Philippines and almost all of them belong to the Philippine subgroup of the Austronesian language family. In September 2012, La Union became the first province in Philippine history to pass an ordinance proclaiming a local language. It declared Ilocano as an official language. This move aims to protect and revitalize the use of Ilocano in various government and civil affairs within the province.

The Filipino Sign Language is designated as the "national sign language of the Filipino deaf" as well as the official sign language for transactions of the Philippine government.

Poland

Article 27 of the Constitution states: "Polish shall be the official language in the Republic of Poland".

Portugal

Portuguese is the sole official language of Portugal.

Romania

The official and national language of Romania is the Romanian language.

Russia

The Russian language is the only national language of Russia and had federal official status, but 27 other languages are considered official in different Federal subjects of Russia.

Serbia

The Serbian language (a variety of Serbo-Croatian) is the national language of Serbia, written in the Cyrillic script. There are 15 minority languages.

Singapore

Singapore has four official languages: English (Singapore English variety), Chinese (Singaporean Mandarin variety), Malay and Tamil. Although English is the primary language of business, government, and education, Malay is designated as the national language. This is due the recognition of ethnic Malays (approximately 14% of the population) as the indigenous peoples of Singapore.

Traditionally, the lingua franca among the different ethnic groups in Singapore was Bazaar Malay, a Malay-based creole. Since independence, the government has been promoting English as the main language of Singapore. The bilingual education policy requires students to study two languages: English and a "mother tongue" corresponding to the student's ethnicity. Malay is only offered to non-Malay students as an optional third language in secondary schools. As a result, English has displaced Bazaar Malay as the common language among Singaporeans. Therefore, despite the status of Malay as the national language, the majority doesn't speak it as a first language.

Slovakia

The Slovak language is the national language of Slovakia.

Slovenia

The Slovene language is the national language of Slovenia. There are 6 minority languages.

South Africa

South Africa has 11 official languages, namely Afrikaans, English, isiNdebele, Sepedi, Sesotho, siSwati, Setswana, Xitsonga, Thsivenda, isiXhosa and isiZulu.

The South African constitution further explicitly supports the promotion of the indigenous Khoi, Nama, and San languages; Sign language; community languages such as German, Greek, Gujarati, Hindi, Portuguese, Tamil, Telugu, Urdu; and languages used for religious purposes such as Arabic, Hebrew, Sanskrit.

Spain

Spain has one national constitutional language, Spanish or Castilian, but there are four other languages that are co-official in some territories: Galician language in Galicia, Basque in Euskadi and part of Navarre, Catalan language in Catalonia, Balearic Islands and Valencia (as Valencian), and Aranese in Val d'Aran.

Sri Lanka

The Sinhala Language and Tamil are the national languages of Sri Lanka.

Switzerland

The logo of the Swiss Federal administration, in the four national languages of Switzerland.

Switzerland has four national languages: German, French, Italian and Romansh, all of which have official status at the national level within the Federal administration of Switzerland.

A majority (74%) of the population speaks German, while most of the remainder (21%) speak French, and minorities speak Italian (4%) and Romansh (1%, not monolingually). German speakers are predominant in most of the country, while French speakers occupy the western parts near the border with France, and the Italian speakers are situated to the south near the border with Italy, mostly within the Canton of Ticino. The Romansh speakers are concentrated in the Canton of Grisons in the south-east.

Taiwan

A national language in Taiwan is legally defined as "a natural language used by an original people group of Taiwan and the Taiwan Sign Language". This includes Formosan languages, Hakka, Mandarin, Taiwanese Hokkien and Matsu dialect.

During Japanese rule (1895 to 1945), the "national language movement" (國語運動, kokugo undō) promoted the Japanese language. After their defeat in the Chinese Civil War in 1949, the Kuomintang regime of the Republic of China retreated to the island of Taiwan, where they introduced Standard Chinese, which was spoken by few of the island population at the time, to be the "national language". Today however, the National languages development act recognises languages of all people groups of Taiwan to be national languages.

Tunisia

The official language of the Tunisian state is Modern Standard Arabic. However, it is not the mother tongue of the population. Therefore, it is not often used to communicate between Tunisian people, instead Tunisian Arabic plays these roles and is the national language of Tunisia. Furthermore, even without an official status, French is also known by 63.6% of the population. It is used extensively in its written and spoken form in administration, education, and business environments. Berber minorities in the south-west and on Djerba Island also use the Tunisian Chelha language.

Turkey

Turkish is the national language of Turkey per the Turkish constitution.

Uganda

The national language of Uganda is English.

Ukraine

Ukrainian is the only official language of Ukraine.

United Kingdom

The English language (British English) is the de facto official language of the United Kingdom and is the sole language of an estimated 95% of the British population. The three Home Nations outside England have national languages of their own with varying degrees of recognition, which coexist with the dominant English language. Britain also has several Crown Dependencies and Overseas Territories which are to some extent self-governing, but are not recognized as independent states. Many of these have their own regional languages.

Northern Ireland

In Northern Ireland, both the Irish language and the Ulster Scots dialects are recognized by the Good Friday Agreement as "part of the cultural wealth of the island of Ireland" and are promoted by the Foras na Gaeilge (Irish Institute) and Tha Boord o Ulstèr-Scotch (the Ulster-Scots Agency) respectively.

English was the sole official language until 2022 when the Identity and Language (Northern Ireland) Act 2022 was passed which gave Irish official status in Northern Ireland.

Scotland

In Scotland, Scottish Gaelic is a minority language spoken by 57,375 people (1.1% of the Scottish population aged over three years old). The Gaelic Language (Scotland) Act 2005 gives the language a limited official status, and the Bòrd na Gàidhlig is tasked with "securing the status of the Gaelic language as an official language of Scotland commanding equal respect to the English language". Scots, generally treated as a West Germanic language related to but separate from English, has no official status but is recognized as a minority language, and is the language of much Scottish literature, including the poetry of Robert Burns.

Wales

The Welsh language has official status within Wales, and as of the 2011 census, is spoken by 562,000 people, or 19% of the population. The Welsh Language Board (Bwrdd yr Iaith Gymraeg) is legally tasked with ensuring that, "in the conduct of public business and the administration of justice, the English and Welsh languages should be treated on a basis of equality".

Crown Dependencies: Isle of Man

English is de facto the only official language. However a few words of Manx Gaelic (the historical national language) are sometimes encountered in government institutions, largely for symbolic and ceremonial purposes, and it is the main medium of instruction in one primary school.

English regions

Cumbria

English is the main language spoken in the county of Cumbria. Cumbric was the historical language of Cumbria, a Brythonic language closely related to Welsh. It also used to be spoken in parts of Lancashire and southern Scotland. Most say that Cumbric became extinct in the 12th or 13th century. The Cumbric numerical system is still used by many shepherds in the Lake District.

Cornwall

English is the de facto main language spoken in the county of Cornwall. Historically, the main language of Cornwall was Cornish. By 1800, Cornish was endangered with some debate about a mythical last speaker of the Cornish language. Revival of the Cornish language and some recognition has occurred in the 20th century.

United States

In the United States, English (American English) is the national language only in an informal sense, by numbers and by historical and contemporary association. The United States Constitution does not explicitly declare any official language, although the constitution is written in English, as is all federal legislation.

Since 1973, every year, a bill was introduced to the United States Congress by a Representative or a Senator to try to establish English as the official language of the United States.

Vietnam

In Vietnam, the Vietnamese language had been the de facto national language for many years, but it was not until Decree No. 5 of the 2013 constitution that the Vietnamese language was officially described as the National Language.

Corpus callosum

From Wikipedia, the free encyclopedia
Corpus callosum
Corpus callosum from above, front part at the top of the image.

Sagittal section of brain, front part to the left. The corpus callosum can be seen in the center, in light gray

The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mammals. It spans part of the longitudinal fissure, connecting the left and right cerebral hemispheres, enabling communication between them. It is the largest white matter structure in the human brain, about 10 in (250 mm) in length and consisting of 200–300 million axonal projections.

A number of separate nerve tracts, classed as subregions of the corpus callosum, connect different parts of the hemispheres. The main ones are known as the genu, the rostrum, the trunk or body, and the splenium.

Structure

MRI of corpus callosum and its named parts
Corpus callosum

The corpus callosum forms the floor of the longitudinal fissure that separates the two cerebral hemispheres. Part of the corpus callosum forms the roof of the lateral ventricles.

The corpus callosum has four main parts – individual nerve tracts that connect different parts of the hemispheres. These are the rostrum, the genu, the trunk or body, and the splenium. A narrowed part between the trunk and the splenium is known as the isthmus. Fibres from the trunk and the splenium known together as the tapetum form the roof of each lateral ventricle.

The front part of the corpus callosum, towards the frontal lobes, is called the genu ("knee"). The genu curves downward and backward in front of the septum pellucidum, diminishing greatly in thickness. The lower, much thinner part is the rostrum and is connected below with the lamina terminalis, which stretches from the interventricular foramina to the recess at the base of the optic stalk. The rostrum is named for its resemblance to a bird's beak.

The end part of the corpus callosum, towards the cerebellum, is called the splenium. This is the thickest part, and overlaps the tela choroidea of the third ventricle and the midbrain, and ends in a thick, convex, free border. Splenium translates as "bandage" in Greek.

The trunk of the corpus callosum lies between the splenium and the genu.

The callosal sulcus separates the corpus callosum from the cingulate gyrus.

Relations

On either side of the corpus callosum, the fibers radiate in the white matter and pass to the various parts of the cerebral cortex; those curving forward from the genu into the frontal lobes constitute the forceps minor (also forceps anterior) and those curving backward from the splenium into the occipital lobes, the forceps major (also forceps posterior). Between these two parts is the main body of the fibers, which constitute the tapetum and extend laterally on either side into the temporal lobe, and cover in the central part of the lateral ventricle. The tapetum and anterior commissure share the function of connecting left and right temporal lobes.

The anterior cerebral arteries are in contact with the undersurface of the rostrum; they arch over the front of the genu and are carried along the trunk, supplying the front four-fifths of the corpus callosum.

Neuronal fibers

The size, amount of myelination, and density of the fibers in the subregions relate to the functions of the brain regions they connect. Myelination is the process of coating neurons with myelin, which helps the transfer of information between neurons. The process is believed to occur until an individual's thirties with peak growth in the first decade of one's life. Thinner, lightly myelinated fibers are slower conducting and they connect the association and prefrontal areas. Thicker and fast-conducting fibers connect the visual and motor areas.

The tractogram pictured shows the nerve tracts from six segments of the corpus callosum, providing linking of the cortical regions between the cerebral hemispheres. Those of the genu are shown in coral; of the premotor, green; of the sensory-motor, purple; of the parietal, pink; of the temporal, yellow; and of the splenium, blue.

Thinner axons in the genu connect the prefrontal cortex between the two halves of the brain; these fibers arise from a fork-like bundle of fibers from the tapetum, the forceps minor. Thicker axons in the trunk of the corpus callosum, interconnect areas of the motor cortex, with proportionately more of the corpus callosum dedicated to supplementary motor regions including Broca's area. The splenium, communicates somatosensory information between the two halves of the parietal lobe and the visual cortex at the occipital lobe, these are the fibers of the forceps major.

A study of five- to eighteen-year-olds found a positive correlation between age and callosal thickness.

Variation between sexes

The corpus callosum and its relation to sex has been a subject of debate in the scientific and lay communities for over a century. Initial research in the early 20th century claimed the corpus to be different in size between men and women. That research was, in turn, questioned, and ultimately gave way to more advanced imaging techniques that appeared to refute earlier correlations. However, advanced analytical techniques of computational neuroanatomy developed in the 1990s showed that sex differences were clear, but confined to certain parts of the corpus callosum, and that they correlated with cognitive performance in certain tests. An MRI study found that the midsagittal corpus callosum cross-sectional area is, after controlling for brain size, on average, proportionately larger in females.

Using diffusion tensor sequences on MRI machines, the rate at which molecules diffuse in and out of a specific area of tissue, anisotropy can be measured and used as an indirect measurement of anatomical connection strength. These sequences have found consistent sex differences in human corpus callosal shape and microstructure.

Analysis by shape and size has also been used to study specific three-dimensional mathematical relationships with MRIs, and have found consistent and statistically significant differences between sexes. Specific algorithms have found significant differences between the two sexes in over 70% of cases in one review.

A 2005 study on the sizes and structures of the corpus callosum in transgender people found it to be structurally more in line with their declared gender than their assigned sex. 

Correlates of size with handedness

One study reported that the front portion of the human corpus callosum was 0.75 cm2 or 11% larger in left-handed and ambidextrous people than right-handed people. This difference was evident in the anterior and posterior regions of the corpus callosum, but not in the splenium. However, a 2022 meta-analysis failed to confirm any substantial differences in the corpus callosum related to left vs. right- vs. mix-handedness. Others have instead suggested that the degree of handedness negatively correlates with the size of the corpus callosum, meaning that individuals who are capable of using both hands with dexterity would have the largest corpus callosum and vice versa for either left or right hand.

Clinical significance

Epilepsy

Electroencephalography is used to find the source of electrical activity causing a seizure as part of the surgical evaluation for a corpus callosotomy.

The symptoms of refractory (difficult to treat) epilepsy can be reduced by cutting through the corpus callosum in an operation known as a corpus callosotomy lobotomy paralysis. This is usually reserved for cases in which complex or grand mal seizures are produced by an epileptogenic focus on one side of the brain, causing an interhemispheric electrical storm. The diagnostic work up for this procedure involves an electroencephalogram, MRI, PET scan, and evaluation by a neurologist, neurosurgeon, psychiatrist, and neuroradiologist before a partial lobotomy surgery can be considered.

Failure to develop

The formation of the corpus callosum begins with the first midline crossing of pioneer axons around week 12 in the prenatal development of the human, or day 15 in the embryogenesis of the mouse. Agenesis of the corpus callosum (ACC) is a rare congenital disorder that is one of the most common brain malformations observed in human beings, in which the corpus callosum is partially or completely absent. ACC is usually diagnosed within the first two years of life, and may manifest as a severe syndrome in infancy or childhood, as a milder condition in young adults, or as an asymptomatic incidental finding. Initial symptoms of ACC usually include seizures, which may be followed by feeding problems and delays in holding the head erect, sitting, standing, and walking. Other possible symptoms may include impairments in mental and physical development, hand-eye coordination, and visual and auditory memory. Hydrocephaly may also occur. In mild cases, symptoms such as seizures, repetitive speech, or headaches may not appear for years. Some syndromes often associated with ACC include Aicardi syndrome, Andermann syndrome, Shapiro syndrome, and acrocallosal syndrome.

ACC is usually not fatal. Treatment usually involves management of symptoms, such as hydrocephaly and seizures, if they occur. Although many children with the disorder lead normal lives and have average intelligence, careful neuropsychological testing reveals subtle differences in higher cortical function compared to individuals of the same age and education without ACC. Children with ACC accompanied by developmental delay and/or seizure disorders should be screened for metabolic disorders.

In addition to agenesis of the corpus callosum, similar conditions are hypogenesis (partial formation), dysgenesis (malformation), and hypoplasia (underdevelopment, including too thin).

Other studies have also linked possible correlations between corpus callosum malformation and autism spectrum disorders.

Kim Peek, a savant and the inspiration behind the movie Rain Man, was found with agenesis of the corpus callosum, as part of FG syndrome.

Other disease

Anterior corpus callosum lesions may result in akinetic mutism or anomic aphasia. See also:

History

The first study of the corpus with relation to gender was by R. B. Bean, a Philadelphia anatomist, who suggested in 1906 that "exceptional size of the corpus callosum may mean exceptional intellectual activity" and that there were measurable differences between men and women. Perhaps reflecting the political climate of the times, he went on to claim differences in the size of the callosum across different races. His research was ultimately refuted by Franklin Mall, the director of his own laboratory.

Of more mainstream impact was a 1982 Science article by Holloway and Utamsing that suggested sex difference in human brain morphology, which related to differences in cognitive ability. Time published an article in 1992 that suggested that, because the corpus is "often wider in the brains of women than in those of men, it may allow for greater cross-talk between the hemispheres—possibly the basis for women’s intuition."

Later publications in the psychology literature have raised doubt as to whether the anatomic size of the corpus is actually different. A meta-analysis of 49 studies since 1980 found that, contrary to de Lacoste-Utamsing and Holloway, no sex difference could be found in the size of the corpus callosum, whether or not any account was taken of larger male brain size. A study in 2006 using thin slice MRI showed no difference in thickness of the corpus when accounting for the size of the subject.

Other animals

The corpus callosum is found only in placental mammals, while it is absent in monotremes and marsupials, as well as other vertebrates such as birds, reptiles, amphibians and fish. (Other groups do have other brain structures that allow for communication between the two hemispheres, such as the anterior commissure, which serves as the primary mode of interhemispheric communication in marsupials, and which carries all the commissural fibers arising from the neocortex (also known as the neopallium), whereas in placental mammals, the anterior commissure carries only some of these fibers.) In primates, the speed of nerve transmission depends on its degree of myelination, or lipid coating. This is reflected by the diameter of the nerve axon. In most primates, axonal diameter increases in proportion to brain size to compensate for the increased distance to travel for neural impulse transmission. This allows the brain to coordinate sensory and motor impulses. However, the scaling of overall brain size and increased myelination have not occurred between chimpanzees and humans. This has resulted in the human corpus callosum's requiring double the time for interhemispheric communication as a macaque's. The fibrous bundle at which the corpus callosum appears, can and does increase to such an extent in humans that it encroaches upon and wedges apart the hippocampal structures.

Environmental toxicology

From Wikipedia, the free encyclopedia
Overview of the interdisciplinarity of environmental toxicology
Categories of organisms commonly used for assessing environmental toxicity

Environmental toxicology is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms. Ecotoxicology is a subdiscipline of environmental toxicology concerned with studying the harmful effects of toxicants at the population and ecosystem levels.

Rachel Carson is considered the mother of environmental toxicology, as she made it a distinct field within toxicology in 1962 with the publication of her book Silent Spring, which covered the effects of uncontrolled pesticide use. Carson's book was based extensively on a series of reports by Lucille Farrier Stickel on the ecological effects of the pesticide DDT.

Organisms can be exposed to various kinds of toxicants at any life cycle stage, some of which are more sensitive than others. Toxicity can also vary with the organism's placement within its food web. Bioaccumulation occurs when an organism stores toxicants in fatty tissues, which may eventually establish a trophic cascade and the biomagnification of specific toxicants. Biodegradation releases carbon dioxide and water as by-products into the environment. This process is typically limited in areas affected by environmental toxicants.

Harmful effects of such chemical and biological agents as toxicants from pollutants, insecticides, pesticides, and fertilizers can affect an organism and its community by reducing its species diversity and abundance. Such changes in population dynamics affect the ecosystem by reducing its productivity and stability.

Although legislation implemented since the early 1970s had intended to minimize harmful effects of environmental toxicants upon all species, McCarty (2013) has warned that "longstanding limitations in the implementation of the simple conceptual model that is the basis of current aquatic toxicity testing protocols" may lead to an impending environmental toxicology "dark age".

Governing policies on environmental toxicity

U.S. policies

To protect the environment, the National Environmental Policy Act (NEPA) was written. The main point that NEPA brings to light is that it "assures that all branches of government give proper consideration to the environment prior to undertaking any major federal actions that significantly affect the environment." This law was passed in 1970 and also founded the Council on Environmental Quality (CEQ). The importance of CEQ was that it helped further push policy areas.

CEQ created environmental programs including the Federal Water Pollution Control Act (RCRA), Toxic Substance Control Act, Resources Conservation and Recovery Act (RCRA and the Safe). CEQ was essential in creating the foundation for most of the "current environmental legislation except for Superfund and asbestos control legislation."

Some initial impacts of NEPA pertain to the interpretation within Courts. Not only did Courts interpret NEPA to expand over direct environmental impacts from any projects, specifically federal, but also indirect actions from federal projects.

Toxic Substance Control Act

TSCA, also known as the Toxic Substance Control Act, is a federal law that regulates industrial chemicals that have the potential to be harmful to humans and the environment. TSCA specifically targets "the manufacture, importation, storage, use, disposal, and degradation of chemicals in commercial use." The EPA allows the following to be done: "1. Pre-manufacture testing of chemicals to determine health or environmental risk 2. Review of chemicals for significant risk prior to the start of commercial production 3. Restriction or prohibition on the production or disposal of certain chemicals 4. Import and export control of chemicals prior to their entering or leaving the USA."

The Clean Air Act

The Clean Air Act was aided by the signing of the 1990 amendments. These amendments protected reducing acid, the ozone layer, improving air quality and toxic pollutants. The Clean Air Act was actually revised and with, support from President George H.W Bush, it was signed in. The biggest major threats that this act targets are: urban air pollution, toxic air emissions, stratospheric ozone, acid rain etc. Apart from targeting these specific areas, it also established a national operating that "permits program to make the law more workable, and strengthened enforcement to help ensure better compliance with the Act."

Regulations and enforcement actions on PCBs

As mentioned above, though the United States did ban the use of PCBs, there is the possibility that they are present in products made before the PCB ban in 1979. The Environmental Protection Agency (EPA) released its ban on PCBs on April 19, 1979. According to the EPA, "Although PCBs are no longer being produced in this country, we will now bring under control the vast majority of PCBs still in use," said EPA Administrator Douglas M. Castle. "This will help prevent further contamination of our air, water and food supplies from a toxic and very persistent man-made chemical."

PCBs has been tested on laboratory animals and have caused cancer and birth defects. PCB is suspected of having certain effects on liver and skin of humans. They are also suspected of causing cancer as well. EPA "estimates that 150 million pounds of PCBs are dispersed throughout the environment, including air and water supplies; an additional 290 million pounds are located in landfills in this country." Again, even though they have been banned, there is still a large amount of PCBs are circulating within the environment and are possibly causing effects on the skin and liver of humans.

There were some cases in which people or companies that disposed of PCBs incorrectly. Up until now, there have been four cases in which EPA had to take legal actions against people/companies for their methods of disposal. The two cases involving the companies, were fined $28,600 for improper disposal. It is unknown what fined was charged against the three people for "illegally dumping PCBs along 210 miles of roadway in North Carolina."

Though PCBs were banned, there are some exceptions where they are being used. The area in which it has been completely prohibited is "the manufacture, processing, distribution in commerce, and "non-enclosed" (open to the environment) uses of PCBs unless specifically authorized or exempted by EPA. "Totally enclosed" uses (contained, and therefore exposure to PCBs is unlikely) will be allowed to continue for the life of the equipment." In terms of electrical equipment containing PCBs is allowed under specific controlled conditions. Out of the 750 million pounds of PCBs, electrical equipment represents 578 million pounds. Any new manufacture of PCB is prohibited.

Sources of environmental toxicity

There are many sources of environmental toxicity that can lead to the presence of toxicants in our food, water and air. These sources include organic and inorganic pollutants, pesticides and biological agents, all of which can have harmful effects on living organisms. There can be so called point sources of pollution, for instance the drains from a specific factory, but also non-point sources (diffuse sources) like the rubber from car tires that contain numerous chemicals and heavy metals that are spread in the environment.

PCBs

Polychlorinated biphenyls (PCBs) are organic pollutants that are still present in our environment today, despite being banned in many countries, including the United States and Canada. Due to the persistent nature of PCBs in aquatic ecosystems, many aquatic species contain high levels of this chemical. For example, wild salmon (Salmo salar) in the Baltic Sea have been shown to have significantly higher PCB levels than farmed salmon as the wild fish live in a heavily contaminated environment.

PCBs pertains to a group of human-produced "organic chemicals known as Chlorinated hydrocarbons" The chemical and physical properties of a PCS determine the quantity and location chlorine and unlike other chemicals, they have no form of identification. The range of toxicity is not consistent and because PCBs have certain properties ( chemical stability, non-flammability) they have been used in a colossal amount of commercial and industrial practices. Some of those include, "Electrical, heat transfer and hydraulic equipment, plasticizers in paints, plastics and rubber products and pigments, dyes and carbonless copy paper" to name a few.

Heavy metals

Heavy metals found in food sources, such as fish, can also have harmful effects. These metals can include mercury, lead and cadmium. It has been shown that fish (i.e. rainbow trout) exposed to higher cadmium levels and grow at a slower rate than fish exposed to lower levels or none. Moreover, cadmium can potentially alter the productivity and mating behaviours of these fish.

Heavy metals can also alter the genetic makeup in aquatic organisms. In Canada, a study examined genetic diversity in wild yellow perch along various heavy metal concentration gradients in lakes polluted by mining operations. Researchers wanted to determine what effect metal contamination had on evolutionary responses among populations of yellow perch. Along the gradient, genetic diversity over all loci was negatively correlated with liver cadmium contamination. Additionally, there was a negative correlation observed between copper contamination and genetic diversity. Some aquatic species have evolved heavy metal tolerances. In response to high heavy metal concentrations a Dipteran species, Chironomus riparius, of the midge family, Chironomidae, has evolved to become tolerant to cadmium toxicity in aquatic environments. Altered life histories, increased cadmium excretion, and sustained growth under cadmium exposure is evidence that shows that C. riparius exhibits genetically based heavy metal tolerance.

Radiation

Radiation is given off by matter as either rays or waves of pure energy or high-speed particles. Rays or waves of energy, also known as electromagnetic radiation, include sunlight, X-rays, radar, and radio waves. Particle radiation includes alpha and beta particles and neutrons. When humans and animals are exposed to high radiation levels, they can develop cancer, congenital disabilities, or skin burns. Plants also face problems when exposed to large levels of radiation. After the Chernobyl disaster in 1986, the nuclear radiation damaged the surrounding plants' reproductive tissues, and it took approximately three years for these plans to regain their reproductive abilities. The study of radiation and its effects on the environment is known as radioecology.

Metals toxicity

The most known or common types of heavy metals include zinc, arsenic, copper, lead, nickel, chromium and cadmium. All of these types cause certain risks on human and environment health.

Though certain amount of these metals can actually have an important role in, for example, maintaining certain biochemical and physiological, "functions in living organisms when in very low concentrations, however they become noxious when they exceed certain threshold concentrations." Heavy metal are a huge part of environmental pollutions and their toxicity "is a problem of increasing significance for ecological, evolutionary, nutritional and environmental reasons."

Person has been exposed to arsenic poisoning through contaminated water

Arsenic

Arsenic, one of the most important heavy metals, causes ecological problems and health issues in humans. It is "semimetallic property, is prominently toxic and carcinogenic, and is extensively available in the form of oxides or sulfides or as a salt of iron, sodium, calcium, copper, etc." It is also one of the most abundant elements on earth and its specific inorganic forms are very dangerous to living creatures (animals, plants, and humans) and the environment.

In humans, arsenic can cause cancer in the bladder, skin, lungs and liver. One of the major sources of arsenic exposure in humans is contaminated water, which is a problem in more than 30 countries in the world.

Humans tend to encounter arsenic by "natural means, industrial source, or from unintended sources." Water can become contaminated by arsenical pesticides or natural arsenical chemicals. There are some cases in which arsenic has been used in suicide attempts and can result in acute poisoning. Arsenic "is a protoplastic poison since it affects primarily the sulphydryl group of cells causing malfunctioning of cell respiration, cell enzymes and mitosis."

Lead

Another extremely toxic metal, lead can and has been known to cause "extensive environmental contamination and health problems in many parts of the world." The physical appearance of lead is bright and silver colored metal. Some sources of lead pollution in the environment include Metal plating and fishing operations, soil waste, factory chimneys, smelting of ores, wastes from batter industries, fertilizers and pesticides and many more. Unlike, other metals such as copper, lead only plays a physiological aspect and no biological functions. In the US, "more than 100 to 200,000 tons of lead per year is being released from vehicle exhausts" and some can be brought in by plants, flow in water or fixation into the soil.

Humans come in contact with lead through mining, fossil fuel burning. In burning, lead and its compounds are exposed into air, soil, and water. Lead can have different effects on the body and effects the central nervous system. Someone who has come in contact with lead can have either acute or chronic lead poisoning. Those who experience acute poisoning have symptoms such as appetite, headache, hypertension, abdominal pain, renal dysfunction, fatigue, sleeplessness, arthritis, hallucinations and vertigo." Chronic exposure on the other hand, can cause more severe symptoms such as, "mental retardation, birth defects, psychosis, autism, allergies, dyslexia, weight loss, hyperactivity, paralysis, muscular weakness, brain damage, kidney damage and may even cause death."

Mercury

Mercury, a shiny silver-white, can transform into a colorless and odorless gas when heated up. Mercury highly affects the marine environment and there have been many studies conducted on the effects on the water environment. The biggest sources of mercury pollution include "agriculture, municipal wastewater discharges, mining, incineration, and discharges of industrial wastewater" all relatively connected to water.

Mercury exists in three different forms and all three possess different levels of bioavailability and toxicity. The three forms include organic compounds, metallic elements and inorganic salts. As stated above, they are present in water resources such as oceans, rivers and lakes. They are absorb by microorganism, and go through, "biomagnification causing significant disturbance to aquatic lives."

Mercury hurts marine life but can also be very hurtful towards humans' nervous system. Higher levels of mercury exposure can change many brain functions. It can "lead to shyness, tremors, memory problems, irritability, and changes in vision or hearing."

Cadmium

According to, ATSDR ranking, cadmium is the 7th most toxic heavy metal. Cadmium is interesting in that once it is exposed to humans (at work) or animals in their environment, it will accumulate inside the body throughout the life of the human/animal. Though cadmium was used as replacement for tin in WWI and pigment in paint industries back in the day, currently it is seen mostly in rechargeable batteries, tobacco smoke and some alloys production.

As stated by the Agency for Toxic Substance and Disease Registry, in " the US, more than 500,000 workers get exposed to toxic cadmium each year." It is also stated that the highest exposure to cadmium can be seen in China and Japan.

The effects of cadmium on the kidney and bones is huge. It can cause bone mineralization which "is the process of laying down minerals on a matrix of the bone". This can happen through renal dysfunction or bone damage.

Chromium

The 7th most abundant element, chromium, can occur naturally when one burns oil and coal and is released into the environment through sewage and fertilizers. Chromium usage can be seen in, "industries such as metallurgy, electroplating, production of paints and pigments, tanning, wood preservation, chemical production and pulp and paper production." Chromium toxicity affects the "biological processes in various plants such as maize, wheat, barley, cauliflower, citrullus and in vegetables. Chromium toxicity causes chlorosis and necrosis in plants."

Pesticides

Pesticides are a major source of environmental toxicity. These chemically synthesized agents have been known to persist in the environment long after their administration. The poor biodegradability of pesticides can result in bioaccumulation of chemicals in various organisms along with biomagnification within a food web. Pesticides can be categorized according to the pests they target. Insecticides are used to eliminate agricultural pests that attack various fruits and crops. Herbicides target herbal pests such as weeds and other unwanted plants that reduce crop production.

DDT

Dichlorodiphenyltrichloroethane (DDT) is an organochlorine insecticide that has been banned due to its adverse effects on both humans and wildlife. DDT's insecticidal properties were first discovered in 1939. Following this discovery, DDT was widely used by farmers in order to kill agricultural pests such as the potato beetle, codling moth and corn earworm. In 1962, the harmful effects of the widespread and uncontrolled use of DDT were detailed by Rachel Carson in her book The Silent Spring. Such large quantities of DDT and its metabolite dichlorodiphenyldichloroethylene (DDE) that were released into the environment were toxic to both animals and humans.

DDT is not easily biodegradable and thus the chemical accumulates in soil and sediment runoff. Water systems become polluted and marine life such as fish and shellfish accumulate DDT in their tissues. Furthermore, this effect is amplified when animals who consume the fish also consume the chemical, demonstrating biomagnification within the food web. The process of biomagnification has detrimental effects on various bird species because DDT and DDE accumulate in their tissues inducing egg-shell thinning. Rapid declines in bird populations have been seen in Europe and North America as a result.

Humans who consume animals or plants that are contaminated with DDT experience adverse health effects. Various studies have shown that DDT has damaging effects on the liver, nervous system and reproductive system of humans.

By 1972, the United States Environmental Protection Agency (EPA) banned the use of DDT in the United States. Despite the regulation of this pesticide in North America, it is still used in certain areas of the world. Traces of this chemical have been found in noticeable amounts in a tributary of the Yangtze River in China, suggesting the pesticide is still in use in this region.

Though DDT was banned in 1972, some of the pesticide (as well as other chemical) lingered in the environment. This lingering of toxic material led to the near extinction of peregrine falcon. There was high levels of DDT were found in many areas such as "eggs, fat and tissues of the bird." The government . worked with conservation groups in helping them breed out of the contaminated area. Finally, in 1999 the birds were taken off the U.S endangered species list.

Sulfuryl fluoride

Sulfuryl fluoride is an insecticide that is broken down into fluoride and sulfate when released into the environment. Fluoride has been known to negatively affect aquatic wildlife. Elevated levels of fluoride have been proven to impair the feeding efficiency and growth of the common carp (Cyprinus carpio). Exposure to fluoride alters ion balance, total protein and lipid levels within these fish, which changes their body composition and disrupts various biochemical processes.

PFAS chemicals

Per and poly fluoroalkyl substances, known as PFAS, are a group of approximately 15 000 chemicals. The common structure of these chemicals involves a functional group and a long carbon tail that is fully or partially fluorinated. The first PFAS chemical, polytetrafluoroethylene (PTFE), was accidentally synthesized in 1938 by DuPont researcher Roy J. Plunkett while making refrigerants. The chemical was found to have unique and useful properties such as resistance to water, oil, and extreme temperatures. In 1945 DuPont patented this chemical, along with other PFAS chemicals like PFOA with the now household name, Teflon. American multinational conglomerate 3M began mass producing Teflon in 1947. Then in the 1960's, the US navy and 3M created a new type of fire-fighting foam using PFAS chemicals, “aqueous film-forming foam” or AFFF, which was then shipped around the world and used at airports, military sites, and fire-fighting training centers. The chemicals are now used in many household products including nail polish, makeup, shampoos, soaps, toothpastes, menstrual products, clothes, contact lenses and toilet paper. The chemicals are also used in fracking, artificial grass, lubricants (mechanical, industrial and bicycle), food packaging, magazines, pesticides, refrigerants, and even surgically implanted medical devices.

These chemicals have been given the nickname "forever chemicals" due to their extreme stability and resistance to natural degradation in the environment. They also bioaccumulate in humans and animals, with many of the PFAS chemicals having half-lives of several years. The also "biomagnify", so animals higher in the food chain tend to have higher concentration of the chemicals in their blood. PFAS has been found in almost all human blood samples tested, one study found 97% of Americans has PFAS in their blood. PFAS chemicals have been linked to high cholesterol, altered kidney and thyroid function, ulcerative colitis, immunosuppression, decreased effectiveness of vaccines, low birth weight, reproductive issues, and cancers such as kidney, testicular and liver cancer. However, we are still uncovering the full health effects of these chemicals.

PFAS chemicals are now ubiquitous in the environment, recent research found PFAS chemicals in all rain water studied. DuPont and 3M had both done internal studies on the potential harmful effects of these chemicals, and had known for decades of their potential to cause cancers and low birth weight. Yet this research was not made public and the companies continued to make large profits off the harmful chemicals. In 2000 3M announced they will voluntarily halt production of PFOA and PFOS — technically known as “long-chain” chemicals — and will stop putting them in products by 2002. They replaced these chemicals with new “short-chain” PFAS formulations, but scientists have found these replacements to be possibly just as hazardous.

Lawsuits around the world have now sprung up against companies and governments who knew of the harm these chemicals could do and continued to use them. Regulation talks on these chemicals is now happening world-wide. Remediation of these "forever chemicals" has been attempted in hot spots around the world, by placing the contaminated soil in landfill or heating at extremely high temperature. However, these are both very expensive, and new, cheaper remediation tools are desperately required.

Cyanobacteria and cyanotoxins

Cyanobacteria, or blue-green algae, are photosynthetic bacteria. They grow in many types of water. Their rapid growth ("bloom") is related to high water temperature as well as eutrophication (resulting from enrichment with minerals and nutrients often due to runoff from the land that induces excessive growth of these algae). Many genera of cyanobacteria produce several toxins. Cyanotoxins can be dermatotoxic, neurotoxic, and hepatotoxic, though death related to their exposure is rare. Cyanotoxins and their non-toxic components can cause allergic reactions, but this is poorly understood. Despite their known toxicities, developing a specific biomarker of exposure has been difficult because of the complex mechanism of action these toxins possess.

Cyanotoxins in drinking water

The occurrence of this toxin in drinking water depends on a couple of factors. One, is the drinking water's level in raw source water and secondly, it depends on the effectiveness of removing these toxins from water when drinking water is actually being produced. Due to being no data on the absence/presence of these toxins in drinking water, it is very hard to actually monitor the amounts that are present in finished water. This is a result of the U.S not having state or federal programs in place that actually monitor the presence of this toxins in drinking water treatment plants.

Effects on humans

Though data on the effects of these two toxins are limited, from what is available it suggests the toxins attack the liver and kidney. There was an hepatoenteritis-like outbreak in Palm Island, Australia (1979), due to the consumption of water that contained, "C. raciborskii, a cyanobacteria that can produce cylindrospermopsin." Most cases (typically involving children) have required they be taken to a hospital. The results of hospitilation include: Vomiting, kidney damage (due to lose of water, protein and electrolytes) fever, bloody diarrhea, and headaches.

Agent-based model

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Agent-based_model An agent-based model ( A...