2. FORMALIN AND ITS EFFECT ON HEALTH
Formalin is a solution made up of 37% formaldehyde by weight, which is stabilized by the addition of methanol. If used in sufficiently low quantities, it does have legitimate commercial uses, for example, to prevent bacterial growth in fish farms. Nonetheless, in larger doses or with extended exposure, formaldehyde is considered to be toxic and cancer causing. Formalin is irritating, corrosive and toxic and absorbed from all surfaces of the body. Although the short-term health effects of formaldehyde exposure are well known, less is known about its potential long-term health effects. Regular consumption of formalin-laced fish increases chance of malignancy and neurological impairment or brain functions. The International Agency for Research on Cancer (IARC) says there was sufficient evidence for carcinogenicity in humans. Based on the available evidence, some of these expert agencies have evaluated the cancer-causing potential of formaldehyde. On 10 June 2011, the US National Toxicology Program formally described formaldehyde to be a known carcinogen. The most common result of chronic poisoning caused by formalin is damaged kidneys and cancer. Formalin may cause uncontrolled cell growth or cancer in stomach, lung and respiratory system if anyone consumes fish contaminated with it. A study showed mice exposed to formalin with concentration of 6 to 15 ppm for 2 years developed squamous-cell carcinoma in the nostril [3]. Formalin causes diverse histopathological changes indicating the destruction in the liver tissue and this destruction has direct relationship with the length of the exposure period [4]. It has a harmful effect on reproduction system by inducing oxidative stress [5],[6]. High consumption of formalin could cause damage to the cornea in the eyes and result in loss of vision. Formaldehyde causes inflammation of the linings of the mouth, throat and gastrointestinal tract and eventual ulceration and necrosis of the mucous lining of the gastrointestinal tract producing lesions in the parenchymatous organs [7]. Laboratory studies showed that exposure to formaldehyde could cause nasal cancer in rats. A cohort study of 11,039 textile workers performed by the National Institute for Occupational Safety and Health (NIOSH) also found an association between the duration of exposure to formaldehyde and leukemia deaths [8]. Table 1 shows the summery of negative effects using formalin.