bahaya ubat gegat

Naftalen atau mothballs atau ubat gegat telah diharamkan di Eropah dan China kerana kesan buruk kepada kesihatan. Justeru hindari keluarga anda dari pada menggunakan bahan yang berbahaya kepada kesihatan ini…

Naphthalene

Naphthalene is an organic compound with formula C10H
8. It is the simplest polycyclic aromatic hydrocarbon, and is a whitecrystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass.^[12] As an aromatichydrocarbon, naphthalene's structure consists of a fused pair of benzene rings. It is best known as the main ingredient of traditionalmothballs.

In the early 1820s, two separate reports described a white solid with a pungent odor derived from the distillation of coal tar. In 1821,John Kidd cited these two disclosures and then described many of this substance's properties and the means of its production. He proposed the name naphthaline, as it had been derived from a kind of naphtha (a broad term encompassing any volatile, flammable liquid hydrocarbon mixture, including coal tar).^[13] Naphthalene's chemical formula was determined by Michael Faraday in 1826. The structure of two fused benzene rings was proposed by Emil Erlenmeyer in 1866,^[14] and confirmed by Carl Gräbe three years later.^[15]

A naphthalene molecule can be viewed as the fusion of a pair of benzene rings. (In organic chemistry, rings are fused if they share two or more atoms.) As such, naphthalene is classified as a benzenoid polycyclic aromatic hydrocarbon (PAH). There are two sets of equivalent hydrogen atoms: the alpha positions are numbered 1, 4, 5, and 8 (per diagram in right margin), and the beta positions, 2, 3, 6, and 7. Unlike benzene, the carbon–carbon bonds in naphthalene are not of the same length. The bonds C1−C2, C3−C4, C5−C6 and C7−C8 are about 1.37 Å (137 pm) in length, whereas the other carbon–carbon bonds are about 1.42 Å (142 pm) long. This difference, established by X-ray diffraction,^[16] is consistent with the valence bond model in naphthalene and in particular, with the theorem of cross-conjugation. This theorem would describe naphthalene as an aromatic benzene unit bonded to a diene but not extensively conjugated to it (at least in the ground state). As such, naphthalene possesses several resonance structures. With alkali metals, naphthalene forms the dark blue-green radical anion salts such as sodium naphthalenide, Na⁺C₁₀H₈^-. The naphthalenide salts are strong reducing agents. Naphthalene can be hydrogenated under high pressure in the presence of metal catalysts to give 1,2,3,4-tetrahydronaphthalene.

Exposure to large amounts of naphthalene may damage or destroy red blood cells, most commonly in people with an underlying G6PD (glucose-6-phosphate dehydrogenase) deficiency.^[30] Over 400 million people have an inherited condition called glucose-6-phosphate dehydrogenase deficiency. Humans, in particular children, have developed this condition, known as hemolytic anemia, after ingesting mothballs or deodorant blocks containing naphthalene. Symptoms include fatigue, lack of appetite, restlessness, and pale skin. Exposure to large amounts of naphthalene may cause confusion, nausea, vomiting, diarrhea, blood in the urine, and jaundice (yellow coloration of the skin due to dysfunction of the liver).^[31]

When the US National Toxicology Program (NTP) exposed male and female rats and mice to naphthalene vapors on weekdays for two years,^[32] male and female rats exhibited evidence of carcinogenesis with increased incidences of adenoma and neuroblastoma of the nose, female mice exhibited some evidence of carcinogenesis based on increased incidences of alveolar and bronchiolar adenomas of the lung, and male mice exhibited no evidence of carcinogenesis.

The International Agency for Research on Cancer (IARC)^[33] classifies naphthalene as possibly carcinogenic to humans and animals (Group 2B). The IARC also points out that acute exposure causes cataracts in humans, rats, rabbits, and mice; and that hemolytic anemia (described above) can occur in children and infants after oral or inhalation exposure or after maternal exposure during pregnancy. Under California's Proposition 65, naphthalene is listed as "known to the State to cause cancer".^[34] A probable mechanism for the carcinogenic effects of mothballs and some types of air fresheners containing naphthalene has been identified.^[35][36]

US government agencies have set occupational exposure limits to naphthalene exposure. The Occupational Safety and Health Administration has set a permissible exposure limit at 10 ppm (50 mg/m³) over an eight-hour time-weighted average. The National Institute for Occupational Safety and Health has set a recommended exposure limit at 10 ppm (50 mg/m³) over an eight-hour time-weighted average, as well as a short-term exposure limit at 15 ppm (75 mg/m³).^[37]

Mothballs and other products containing naphthalene have been banned within the EU since 2008.^[38][39]

In China, the use of naphthalene in mothballs is forbidden.^[40] Danger to human health and the common use of natural camphor are cited as reasons for the ban.