Point Reyes National Seashore
Point Reyes National Seashore is a 71, 028-acre park preserve located on the Point Reyes Peninsula in Marin County, California. As a national seashore, it is maintained by the US National Park Service as an important nature preserve, some existing agricultural uses are allowed to continue within the park. All of the beaches were listed as the cleanest in the state in 2010. The fact that the peninsula is on a different tectonic plate than the east shore of Tomales Bay produces a difference in soils and therefore to some extent a noticeable difference in vegetation. The even smaller town of Olema, about 3 miles south of Point Reyes Station, serves as the gateway to the Seashore and its visitor center, the peninsula includes wild coastal beaches and headlands and uplands. The Seashore administers the parts of the Golden Gate National Recreation area, such as the Olema Valley, the northernmost part of the peninsula is maintained as a reserve for Tule Elk, which are readily seen there. The preserve is very rich in raptors and shorebirds.
The Point Reyes Lighthouse attracts whale-watchers looking for the Gray Whale migrating south in mid-January, the Point Reyes Lifeboat Station is a National Historic Landmark. It is the last remaining example of a rail launched lifeboat station that was common on the Pacific coast and this encompasses 5,965 acres along the coast of Drakes Bay. Kule Loklo, a recreated Coast Miwok village, is a walk from the visitor center. The Point Reyes National Seashore attracts 2.5 million visitors annually, hostelling International USA maintains a 45-bed youth hostel at the Seashore. Point Reyes National Seashore Association, formed in 1964, collaborates with the Seashore on maintenance, like underwater parks, these marine protected areas help conserve ocean wildlife and marine ecosystems. A large shellfish farm raising Japanese oysters, Crassostrea gigas, was located in Drakes Estero until, under court order, Court appeals to keep the operation in place were dropped in December,2014. The farm was purchased by the National Park Service in 1972, a federal law enacted in 2009 authorized, but did not require, Interior Secretary Ken Salazar to renew the permit.
The NPS and conservation groups viewed the farm as an inappropriate and environmentally-insensitive use of the estero, the farms supporters argued that it was not ecologically harmful and was important to the local economy. Salazar visited the farm the previous week and phoned the farms owner to give him the news. The oyster farm closure was challenged in U. S. District Court on January 25,2013, the challenge was rejected by a federal court judge, who ruled that the law gave Salazar unfettered discretion to approve or deny a renewal of the permit. The California Coastal Commission voted on February 7,2013 to unanimously approve cease and desist, an attempt to have the appeals court rehear the case was rejected on January 14,2014 and a petition to the United States Supreme Court was denied on June 30,2014
Tomales is a census-designated place on State Route 1 in Marin County, United States. The population was 204 at the 2010 census, the largest employer in Tomales is Tomales High School, which has a student body of approximately 190. Tomales is located above Keys Creek, about 3 mi northeast of Tomales Bay, the nearest city is Petaluma, about 20 minutes away by automobile, and the nearest large city is San Francisco, about 75 minutes to the south. The CDP has an area of 0.33 sq mi. When Europeans first reached Tomales Bay, it was home to Coast Miwok people, numerous authenticated Miwok villages are known from this area, including one sited near the present-day town of Tomales. The Tomalles post office opened in 1854, and changed its spelling to Tomales before 1879, starting in the 1870s, Tomales was a stop on the North Pacific Coast Railroad connecting Cazadero to the Sausalito ferry. Built near the San Andreas Fault, Tomales was affected by the 1906 San Francisco earthquake, one of the towns two cemeteries predates the earthquake, and the damage to the pre-1906 plots shows just how widespread the quakes effects were.
The 2010 United States Census reported that Tomales had a population of 204, the population density was 614.9 people per square mile. The racial makeup of the CDP was 94. 6% White,1. 5% Native American,2. 0% Asian,4. 4% of the population was Hispanic or Latino of any race. The Census reported that 100% of the lived in households. There were 10 unmarried opposite-sex partnerships, and 1 same-sex married couple or partnership,32 households were made up of individuals and 6 had someone living alone who was 65 years of age or older. The average household size was 2.06, there were 58 families, the average family size was 2.55. The median age was 50.5 years, for every 100 females there were 85.5 males. For every 100 females age 18 and over, there were 80.2 males, there were 122 housing units at an average density of 367.7 per square mile, of which 59. 6% were owner-occupied and 40. 4% were occupied by renters. The homeowner vacancy rate was 1. 6%, the vacancy rate was 7. 0%. 61. 8% of the lived in owner-occupied housing units and 38. 2% lived in rental housing units.
As of the census of 2000, there were 210 people,73 households, the population density was 670/sq mi. There were 85 housing units at a density of 271/sq mi
California Bays and Estuaries Policy
The policy is revised as needed. The Pacific coast of California has few natural harbors in comparison to similar lengths of the Atlantic coast of the United States, the policy applies to coastal lagoons and mouths of streams temporarily separated from the ocean by sandbars. The sheltering features making harbors favorable for ocean transportation cargo transfer limit mixing and dilution through surf action, harbors were important foci of early European American settlement of California, and cities have developed adjacent to the larger ones. Unique aquatic ecosystems of limited geographical extent have been impacted by waste disposal practices, exceptions were made for San Francisco Bay and for cooling water discharges at other locations. The policy was revised 16 November 1995
Sir Francis Drake, vice admiral was an English sea captain, navigator and politician of the Elizabethan era. With his incursion into the Pacific he inaugurated an era of privateering, Elizabeth I of England awarded Drake a knighthood in 1581. He was second-in-command of the English fleet against the Spanish Armada in 1588 and he died of dysentery in January 1596 after unsuccessfully attacking San Juan, Puerto Rico. His exploits made him a hero to the English but a pirate to the Spaniards, King Philip II was said to have offered a reward of 20,000 ducats, about £4 million by modern standards, for his life. Francis Drake was born in Tavistock, England, although his birth is not formally recorded, it is known that he was born while the Six Articles were in force. Drake was two and twenty when he obtained the command of the Judith and this would date his birth to 1544. A date of c.1540 is suggested from two portraits, one a miniature painted by Nicholas Hilliard in 1581 when he was allegedly 42 and he was the eldest of the twelve sons of Edmund Drake, a Protestant farmer, and his wife Mary Mylwaye.
The first son was alleged to have named after his godfather Francis Russell. Because of religious persecution during the Prayer Book Rebellion in 1549, there the father obtained an appointment to minister the men in the Kings Navy. He was ordained deacon and was vicar of Upnor Church on the Medway. Drakes father apprenticed Francis to his neighbour, the master of a used for coastal trade transporting merchandise to France. The ship master was so satisfied with the young Drakes conduct that, being unmarried and childless at his death, Francis Drake married Mary Newman in 1569. She died 12 years later, in 1581, in 1585, Drake married Elizabeth Sydenham—born circa 1562, the only child of Sir George Sydenham, of Combe Sydenham, who was the High Sheriff of Somerset. After Drakes death, the widow Elizabeth eventually married Sir William Courtenay of Powderham. At age 23, Drake made his first voyage to the Americas, sailing with his cousin, Sir John Hawkins, on one of a fleet of ships owned by his relatives.
In 1568 Drake was again with the Hawkins fleet when it was trapped by the Spaniards in the Mexican port of San Juan de Ulúa, following the defeat at San Juan de Ulúa, Drake vowed revenge. He made two voyages to the West Indies, in 1570 and 1571, of which little is known, in 1572, he embarked on his first major independent enterprise. He planned an attack on the Isthmus of Panama, known to the Spanish as Tierra Firme and the English as the Spanish Main
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. General Electric took over the company in late 1985 and split it up the following year, after World War I began in August 1914, radio traffic across the Atlantic Ocean increased dramatically after the western Allies cut the German transatlantic telegraph cables. In 1917 the government of the United States took charge of the owned by the major companies involved in radio manufacture in the United States to devote radio technology to the war effort. All production of equipment was allocated to the U. S. Army, U. S. Navy, U. S. Marine Corps. The War Department and the Navy Department sought to maintain a monopoly of all uses of radio technology. The wartime takeover of all radio systems ended late in 1918, the war ended in November of that year. The ending of the governments monopoly in radio communications did not prevent the War. On 8 April 1919, naval Admiral W. H. G.
Bullard, the proposal presented by the government was that if GE created an American-owned radio company, the Army and Navy would effect a monopoly of long-distance radio communications via this company. This marked the beginning of a series of negotiations through which GE would buy the American Marconi company, the Army and the Navy granted RCA the former American Marconi radio terminals that had been confiscated during the War. Admiral Bullard received a seat on the Board of Directors of RCA for his efforts in establishing RCA, the result was federally-created monopolies in radio for GE and the Westinghouse Corporation and in telephone systems for the American Telephone & Telegraph Company. The first chief officer of RCA was Owen D. Young. RCAs incorporation papers required that a majority of its stock be held by American citizens, as the years went on, RCA either took over, or produced for itself, a large number of patents, including that of the superheterodyne receiver invented by Edwin Armstrong.
Over the years, RCA continued to operate international services, under its subsidiary RCA Communications, Inc. GE used RCA as its retail arm for radio sales from 1919, Westinghouse marketed home radios through RCA until 1930. In 1929, RCA purchased the Victor Talking Machine Company, the worlds largest manufacturer of phonographs and this included a majority ownership of the Victor Company of Japan. The new subsidiary became RCA Victor, with Victor, RCA acquired New World rights to the Nipper His Masters Voice trademark. This trademark is used by the British music & entertainment company HMV. RCA began selling the first electronic turntable in 1930, in 1931, RCA Victor began selling 33⅓ rpm records
Russian River (California)
The Russian River, a southward-flowing river, drains 1,485 square miles of Sonoma and Mendocino counties in Northern California. With an annual discharge of approximately 1,600,000 acre feet, it is the second-largest river flowing through the nine-county Greater San Francisco Bay Area. The Russian River springs from the Laughlin Range about 5 mi east of Willits in Mendocino County. It flows generally southward to Redwood Valley, past Calpella, from there the Russian River flows south, past Ukiah and Hopland, and crosses into Sonoma County just north of Cloverdale. Closely paralleled by U. S. Route 101, it descends into the Alexander Valley and it flows south past Cloverdale and Geyserville. East of Healdsburg, Maacama Creek joins the Russian River, after it makes a series of sweeping bends, the Healdsburg Memorial Bridge carries Old Redwood Highway over the river just upstream of U. S. Route 101s Healdsburg crossing. It receives water from Lake Sonoma via Dry Creek, the river turns westward, where it is spanned by the Wohler Bridge, and it is joined by Mark West Creek north of Forestville, followed by Green Valley Creek to the south.
The river passes Rio Nido and Guerneville, in that area, State Route 116 parallels the river, bordering it past Guernewood Park and Monte Rio. Austin Creek enters from the north before the River passes through Duncans Mills, State Route 1 crosses over the river before it flows into the Pacific Ocean between Jenner and Goat Rock Beach. The Russian River estuary is recognized for protection by the California Bays, the mouth is about 60 mi north of the San Francisco Bays Golden Gate bridge. The lower Russian River is a spring, summer. It is very safe at that time for swimming and boating, the river is dangerous in the winter, with swift current and muddy water. The geographer R. S. Holway wrote of the Russian River in his paper The Russian River, the Russian River was one of several rivers draining westward from the Mayacamas Mountains through the Mendocino Plateau to the sea, a region lifted up by tectonic forces. The Navarro River drained from the Cobb Mountain area, while the Russian River drained from the Mt.
St. Helena area, being at a lower elevation, the Russian River began cutting north into the drainage area of the Navarro River. Eroding up a line in Alexander Valley, the Russian River intersected the Navarro River just north of Cloverdale. In one fell swoop, the Russian River took Big Sulphur Creek, the high valleys were eroded into rocky canyons for ten miles north of Cloverdale and for five miles east of Cloverdale. After establishing a connection to Clear Lake, the Russian River was beheaded from Clear Lake by a slide, now Clear Lake flows into the Sacramento River. The river incised a canyon into Fitch Mountain at an early time, the Russian River was prevented from flowing south into San Pablo Bay, due to a 113-foot high ridge at Cotati
Point Arena, California
Point Arena is a small coastal city in Mendocino County, United States. Point Arena is located 31 miles west of Hopland, at an elevation of 118 feet, the population was 449 at the 2010 census, down from 474 at the 2000 census, making it one of the smallest incorporated cities in the state. It is the western most city in the continental United States Its main street comprises part of State Route 1, along with a number of other Mendocino County coastal communities, Point Arena is associated with the hippie and subsequent counterculture groups. Reportedly, the economy is geared toward servicing the summertime tourist industry. The City is near the headquarters of the lands of Manchester Band of Pomo Indians of the Manchester-Point Arena Rancheria. The City is adjacent to the recently formed Point Arena Stornetta Public Lands National Monument, hiking Trails can be accesses at the Point Arena City Hall Parking. Spectacular coastal prairie and ocean views await, of special note is Arena Cove and pier with huge ocean front bluffs showing power of the interface of the Tectonic plates.
The City of Point Arena is located at 38°54′32″N 123°41′35″W and it is in USPS ZIP code 95468. According to the United States Census Bureau, the city has an area of 1.4 square miles. This is the location of the Point Arena Lighthouse, at 115 feet the tallest lighthouse on the West coast of the United States, the lighthouse is the closest location on the mainland to Honolulu, Hawaii at a distance of 2,353 miles. The city has three schools, Point Arena High School, South Coast Continuation High School and the Pacific Community Charter High School. The choice of the school has helped to keep in Point Arena many students who formerly commuted to Mendocino to attend its high school. A variety of fauna and flora occur in the Point Arena area, the location is sometimes a range demarcation for occurrence of some species. For example, the Pacific giant salamander occurs at Point Arena and at points south, the Point Arena State Marine Reserve & Point Arena State Marine Conservation Area are two marine protected areas that extend offshore from Point Arena.
Sea Lion Cove State Marine Conservation Area and Saunders Reef State Marine Conservation Area lie south of Point Arena, like underwater parks, these marine protected areas help conserve ocean wildlife and marine ecosystems. Sound levels in Point Arena are relatively quiet, with locations at night-time dominated by natural sounds such as those of the surf. The maximum acceptable sound level specified in that General Plan Element is 60 Leq for residential areas, Point Arena has cool, wet winters and mild, relatively dry summers. According to the Köppen climate classification system, it has warm-summer Mediterranean climate, the average January temperatures are a maximum of 56.4 °F and a minimum of 40.2 °F
New Albion, known as Nova Albion, was the name of all North America north of Mexico, from sea to sea, claimed by Sir Francis Drake for England in 1579. The extent of New Albion and the location of Drakes port have long debated by historians. Albion is a name for the island of Great Britain. The name may refer to the White Cliffs of Dover, along with Martin Frobishers claims in Greenland and Baffin Island and Drakes claims at the tip of South America, New Albion was one of the earliest English territorial claims in the New World. Like Humphrey Gilberts 1583 claim of Newfoundland, it was followed up by settlement of the Roanoke Colony in 1584, by Jamestown, Virginia in 1607. Assertions that Drake left some of his men behind as a colony in California are based merely on the reduced number who were with him in the Moluccas. Wherever his actual landing place was, it was north of San Diego Bay where Cabrillo had asserted Spains claim. Drake explored the coasts around his port by ship for some time as well as the land on foot.
Upon his return to England on 4 April 1581, Francis Drake was knighted by the French Ambassador on behalf of Queen Elizabeth I for his deeds against the Spanish during the circumnavigational voyage. However, in order to keep a peace with Spain, and to avoid having Spain threaten Englands other claims in the New World, Drakes logs, charts. Thus, the discovery and claim on New Albion was ordered by the Queen to be considered a state secret and his crew were sworn to silence on pain of death. Only years later, after Englands destruction of the Spanish Armada in 1588, an account of the voyage, said to be based on the notes of his chaplain, Francis Fletcher, including many details of New Albion was published in 1628 by Drakes nephew and namesake. After Elizabeths death, maps began to mark the area of North America above Mexico and New Mexico as Nova Albion, although the location of Drakes Port greatly differs among maps. However, Drakes claiming land on the Pacific coast became the basis for subsequent colonial charters issued by English monarchs that purported to grant lands from sea to sea.
Soon afterwards, the Columbia Fur District of the Hudsons Bay Company, the only confirmed sixteenth-century archaeological evidence consists of pieces of porcelain found at Drakes Bay, north of San Francisco. The site of Drakes landing officially recognized by the U. S. Department of the Interior and other bodies is Drakes Cove, the bay is in Marin County, near Point Reyes, just north of the Golden Gate. 38. 034°N122. 941°W /38.034, -122.941 Starting in the seventeenth century, george Vancouver studied Drake’s landing site and concluded it was in Drakes Bay. Drakes Bay, he says, is a harbor in northwest winds
Bodega Bay is a shallow, rocky inlet of the Pacific Ocean on the coast of northern California in the United States. It is approximately 5 mi across and is located approximately 40 mi northwest of San Francisco and 20 mi west of Santa Rosa, the bay straddles the boundary between Sonoma County to the north and Marin County to the south. The bay is a marine habitat used for navigation, Bodega Bay is protected on its north end from the Pacific Ocean by Bodega Head, which shelters the small Bodega Harbor and is separated from the main bay by a jetty. The San Andreas Fault runs parallel to the coastline and bisects Bodega Head, which lies on the Pacific Plate, the village of Bodega Bay sits on the east side of Bodega Harbor. The bay connects on its end to the mouth of Tomales Bay. Streams flowing into Bodega Bay include the Estero de San Antonio, accessible beaches on Bodega Bay include Doran Regional Park and Pinnacle Gulch. Apart from the harbor, all of Bodega Bay lies within the boundaries of the Gulf of the Farallones National Marine Sanctuary, Coast Miwok Native Americans lived on the shores of Bodega Bay.
Documented village names include, Hime-takala, Ho-takala, there is speculation that Bodega Bay may have been Sir Francis Drakes Nova Albion landing location on the California coast. His ship, the Sonora, anchored in the lee of Tomales Point on October 3,1775, Bodega y Quadra named Tomales Bay Puerto de la Bodega. There is no evidence in the journal or on the charts that Bodega y Quadra ever saw the entrance to Bodega Harbor or knew of the lagoon to the north, Bodega y Quadra planned to return, but was not able to. Later, as commandant of the base at San Blas, New Spain, Bodega y Quadra sent other expeditions to Bodega Bay with the intention of establishing a colony. It was decided, that the location was non-ideal, the first Russians to see Bodega Bay were the supervisors of the Aleut hunting parties aboard the American otter hunting ship Peacock in 1807. Timofei Osipovich Tarakanov of the Russian-American Company returned to Novo Arkhangelsk and reported the location to Alexander Andreyevich Baranov, Baranov instructed his assistant Ivan Kuskov to survey the area for a settlement.
Kuskov, the Commerce Counselor of the Russian-American Company sailing in the Kodiak, temporary buildings were erected to house the ships complement of 190 crew The Kodiak remained in Bodega Bay until October 1809, returning to Alaska with more than 2,000 otter pelts. Kuskov returned to Novo Arkhangelsk, reporting abundant fur bearing mammals, timber, Baranov instructed Kuskov to return and establish a permanent settlement in the area. In 1811 Kuskov returned, this time aboard the Chirikov but found fewer otter in Bodega Bay, three American ships were operating in the area from a base in Drakes Bay, sending hunters into San Francisco Bay and the surrounding bays. Zaliv Rumyantsev appears on the earliest Russian charts of Bodega Bay identifying present day Bodega Bay, Bodega Head was named Mouis Rumyantsev. Tomales Point was named Point Great Bodega and Tomales Bay Great Bodega Bay, on his return Kuskov found otter now scarce in Bodega Bay, the harbor having been frequented by numerous American and English otter-hunting expeditions
Point Reyes Station, California
Point Reyes Station is a small unincorporated town located in western Marin County, California. Point Reyes Station is located 13 miles south-southeast of Tomales, at an elevation of 39 feet, Point Reyes Station is located along State Route 1 and is a gateway to the Point Reyes National Seashore, an extremely popular national preserve. About 350 people live in the town, the CDP has a total area of 3.62 sq mi, all land. Point Reyes Station is very close to the San Andreas Fault, at one time, the epicenter of the quake was thought to be near Olema. A walking tour of the fault can be taken from the Point Reyes National Seashores Visitor Center, the place was called Olema Station when the railroad arrived in 1875. The Point Reyes post office opened in 1882, changed its name to Marin in 1891, changed it back to Point Reyes in 1891, the 2010 United States Census reported that Point Reyes Station had a population of 848. The population density was 234.5 people per square mile, the racial makeup of Point Reyes Station was 725 White,7 African American,3 Native American,10 Asian,73 from other races, and 30 from two or more races.
Hispanic or Latino of any race were 155 persons, the Census reported that 100% of the population lived in households. There were 19 unmarried opposite-sex partnerships, and 4 same-sex married couples or partnerships,172 households were made up of individuals and 90 had someone living alone who was 65 years of age or older. The average household size was 2.06, there were 208 families, the average family size was 2.84. The median age was 51.1 years, for every 100 females there were 81.2 males. For every 100 females age 18 and over, there were 81.4 males, there were 490 housing units at an average density of 135.5 per square mile, of which 50. 2% were owner-occupied and 49. 8% were occupied by renters. The homeowner vacancy rate was 0%, the vacancy rate was 6. 8%. 50. 6% of the lived in owner-occupied housing units and 49. 4% lived in rental housing units. As of the census of 2000, there were 818 people,352 households, the population density was 225.1 people per square mile. There were 373 housing units at a density of 102.6 per square mile.
The racial makeup of the CDP in 2010 was 77. 8% non-Hispanic White,0. 6% non-Hispanic African American,1. 1% Asian, hispanic or Latino of any race were 18. 3% of the population. 29. 8% of all households were made up of individuals and 13. 6% had someone living alone who was 65 years of age or older, the average household size was 2.28 and the average family size was 2.83
The Coast Miwok are an indigenous people that was the second largest group of Miwok people. The Coast Miwok inhabited the area of modern Marin County and southern Sonoma County in Northern California, from the Golden Gate north to Duncans Point. The Coast Miwok included the Bodega Bay Miwok from authenticated Miwok villages around Bodega Bay, the Coast Miwok spoke their own Coast Miwok language in the Utian linguistic group. They lived by hunting and gathering, and lived in small bands without centralized political authority, in the springtime they would head to the coasts to hunt salmon and other seafood, including seaweed. When hunting deer, Miwok hunters traditionally used Brewers angelica, Angelica breweri to eliminate their own scent, Miwok did not typically hunt bears. Yerba buena tea leaf were used medicinally, tattooing was a traditional practice among Coast Miwok, and they burned poison-oak for a pigment. Their traditional houses, called kotcha were constructed with slabs of tule grass or redwood bark in a cone-shaped form, Miwok people are skilled at basketry.
A recreated Coast Miwok village called Kule Loklo is located at the Point Reyes National Seashore, the Coast Miwok language is no longer natively spoken, but the Bodega dialect is documented in Callaghan. The original Coast Miwok people world view included animism, and one form of this took was the Kuksu religion that was evident in Central and Northern California. Kuksu was shared with other ethnic groups of Central California, such as their neighbors the Pomo, Ohlone, Esselen. However Kroeber observed less specialized cosmogony in the Miwok, which he termed one of the southern Kuksu-dancing groups, in comparison to the Maidu, Coast Miwok mythology and narratives were similar to those of other natives of Central and Northern California. The Coast Miwok believed in animal and human spirits, and saw the animal spirits as their ancestors, coyote was seen as their ancestor and creator god. In their case the earth began with land formed out of the Pacific Ocean, in their myths, legends and histories, the Coast Miwok participated in the general cultural pattern of Central California.
The authenticated Coast Miwok villages are, On Bodega Bay, Hime-takala, Ho-takala, Tiwut-huya, in this vicinity, Amayelle, Kennekono. On Tomales Bay, Echa-kolum, Shotommo-wi, Utumia At the present-day City of Petaluma, Etem, in this vicinity, Likatiut, Susuli, Wotoki. At the present-day City of San Rafael, Awani-wi, at the present-day City of Sonoma, Huchi. Also in this vicinity, Tuli, Wugilwa, at the present-day City of Cotati, Lumen-takala. At the present-day town of Nicasio, Echa-tamal, at the present-day town of Olema, Olema-loke
A polychlorinated biphenyl is an organic chlorine compound with the formula C12H10−xClx. Polychlorinated biphenyls were once widely deployed as dielectric and coolant fluids in electrical apparatus, carbonless copy paper, because of their longevity, PCBs are still widely in use, even though their manufacture has declined drastically since the 1960s, when a host of problems were identified. The International Research Agency on Cancer, rendered PCBs as definite carcinogens in humans, according to the U. S. Environmental Protection Agency, PCBs cause cancer in animals and are probable human carcinogens. Many rivers and buildings including schools and other sites are contaminated with PCBs, some PCBs share a structural similarity and toxic mode of action with dioxin. Other toxic effects such as endocrine disruption and neurotoxicity are known, the bromine analogues of PCBs are polybrominated biphenyls, which have analogous applications and environmental concerns. The compounds are pale-yellow viscous liquids and they are hydrophobic, with low water solubilities —0.
0027-0.42 ng/L for Aroclors, but they have high solubilities in most organic solvents and fats. They have low vapor pressures at room temperature and they have dielectric constants of 2. 5~2.7, very high thermal conductivity, and high flash points. The density varies from 1.182 to 1.566 kg/L, other physical and chemical properties vary widely across the class. As the degree of chlorination increases, melting point and lipophilicity increase, PCBs do not easily break down or degrade, which made them attractive for industries. PCB mixtures are resistant to acids, oxidation and they can generate extremely toxic dibenzodioxins and dibenzofurans through partial oxidation. Intentional degradation as a treatment of unwanted PCBs generally requires high heat or catalysis, PCBs readily penetrate skin, PVC, and latex. PCB-resistant materials include Viton, polyvinyl acetate, polytetrafluoroethylene, butyl rubber, nitrile rubber, PCBs are derived from biphenyl, which has the formula C12H10, sometimes written 2.
In PCBs, some of the atoms in biphenyl are replaced by chlorine atoms. There are 209 different chemical compounds in which one to ten chlorine atoms can replace hydrogen atoms, PCBs are typically used as mixtures of compounds and are given the single identifying CAS number 1336-36-3. About 130 different individual PCBs are found in commercial PCB products, toxic effects vary depending on the specific PCB. Coplanar or non-ortho The coplanar group members have a rigid structure. They do not activate the AhR, and are not considered part of the dioxin group, because of their lower toxicity, they are of less concern to regulatory bodies. Di-ortho-substituted, non-coplanar PCBs interfere with signal transduction dependent on calcium which may lead to neurotoxicity