Boric acid plays a role as a “stomach poison” for certain pest such as cockroaches, ants and termites. As an insecticide, it usually applied in bait form or used as a dry powder in which containing a feeding attractant and then added into crevices and creaks so that it forms a layer of dust. So boric acid adheres to their legs when the insects move across the powder. Hence, they may ingest the poison when the insects groom themselves. This will causes death due to starvation and dehydration after 3-10 days. However, the insecticide mechanism of boric acid on insects has not been satisfactorily developed. Some hypotheses has been suggested including death by starvation owing to abrasive effect on the cuticle then cause destruction or slow drying of foregut cells[12, 13].
Besides that, when boric acid used as an herbicide, it desiccates or disrupts the photosynthesis system in plants. Hence, boric acid is normally used to suppress algae in swimming pools and sewage systems. On the other hand, as a fungicide, the fungicidal properties of boric acid prevent the production of conidia or asexual spores of the fungi; hence, it suppresses the growth of fungi. Therefore, boric acid is used as wood preservative in wood industry such as lumber and timber products that controls decay producing fungi[9,14].
Boric acid is reported to be used as food preservatives in some foods and food products. Boric acid is used for preserving meats, meat products, caviar and dairy products. This is because boric acid is able to inhibit the growth of microorganism, therefore, the preserved food can stay fresh and longer. Moreover, according to Yiu et al. (2008), boric acid was added to some food products to control starch gelatinization, as well as enhance the color, texture and flavor of the food.
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BA given orally is readily and completely absorbed in humans and animals. In adult human volunteers, Schou et al. found 94% of a single oral dose of 500 mg BA (131 mg B) was excreted via the urine. Jansen et al. evaluated the absorption of a single aqueous dose of 750 mg of BA in a group of six male volunteers; more than 92% of the BA was excreted in the urine. A similar degree of oral absorption based on urinary excretion of B was observed in volunteers drinking curative spa waters with a high B content, providing a daily dose of approx 100 mg B for 2 wk. There is negligible absorption of BA across intact skin in humans and animals. Maibach reported minimal dermal absorption of BA in human volunteers. Earlier studies showed little evidence of dermal absorption in human infants and adults. Dermal absorption across non-intact skin varied with the vehicle used; greater absorption was observed with aqueous-based vehicles compared to oil-based vehicles (e.g., ointments). Only traces of boric acid in ointment penetrated the skin of infants with moderate diaper rash.
BA is distributed similarly in humans and animals. It is rapidly distributed throughout body water. After administration of BA, B levels in soft tissues are equivalent to those found in plasma, whereas bone B levels appear to be higher than those found in plasma or soft tissues. In humans, a greater concentration of B in bone was reported relative to other tissues. Bone B concentrations were determined on 116 ashed samples from 33 human cadavers[25, 26]. More recently, Ward examined B concentrations using a more sophisticated neutron activation analytical technique in a variety of human tissues, including bone, from 14 normal individuals and 18 individuals with rheumatoid arthritis. High B levels were found in bone, hair, and teeth.
BA is not metabolized in humans or animals. The metabolism of BA by biological systems is not possible owing to the high energy requirements (523 kJ/mol) needed to break the B----O bond. In both humans and animals, BA is excreted unchanged in the urine regardless of the route of administration. It is rapidly excreted, with a half-life of < 24 h in humans and animals. BA is slowly eliminated from bone.
In humans, 99% of a single iv dose of BA was excreted in the urine, and the half-life was estimated to be 21 h, based on a three-compartment pharmacokinetic model. In another study by the same investigators, 94% of an oral dose of BA (aqueous solution) was recovered in the urine of a group of male volunteers, and more than 50% of the oral dose was eliminated in the first 24 h, consistent with the 21-h half-life in the iv study.
Because of boric acid contains cumulative toxicity, FAO/WHO Expert Committee declared that boric acid is unsafe to use as food additives. Even though Ministry of Health Malaysia does not allow boric acid to be used as a food additive, however, it has been reported in some of the local foods in Malaysia such as yellow noodle and fish ball. Moreover, boric acid is harmful to human health if consumed in higher amount. However, due to unawareness of the risk of boric acid, it is continued to be used in the production of food especially noodles and some processed seafood such as fish ball. Boric acid normally used for preservation of food products. It can cause to health problem if the food containing boric acid was ingested by human as boric acid and borates are toxic to cell. Hence, it is deleterious to health and its usage is not recommended. For new-born baby, the possible lethal doses are in between 3-6 g, whereas 15-20 g total for adults. The common symptoms from several incidents of boric acid poisoning included coughing, eye irritation, vomiting and oral irritation. However, the toxicity mechanisms of boron compound remain unclear (Kot, 2009). According to Moseman (1994), the usual amount of boron in urine, blood and soft tissues, normally in the range below 0.05 mg kg−1 and do not above 10 mg kg−1. Some boric acid poisoning cases reported that as high as 2 g kg−1 boric acid was found in liver tissue and brain[34, 35].
Boron (B), the fifth element in the periodic chart, is ubiquitous in the environment, where it is found combined with O to form compounds called inorganic borates (e.g., borax). Natural sources of borates in the environment include soils, rocks, surface and ocean waters, and the atmosphere.
B in the form of borates has long been recognized as an essential plant micronutrient for the growth and viability of plants. Recently, there has been a growing body of evidence that B may be an essential element for frogs, fish, rats, and humans, as well as for plants[1-5]. The major sources of B exposure are diet and drinking water. Fruits, vegetables, and nuts are especially rich in B. Rainey et al. recently studied daily dietary B intake, evaluating the food consumption records of over 25,000 Americans over several days. The median, mean, and 95 percentile B intake for all participants were 0.76, 0.93, and 2.4 mg B/d, respectively.
Boric acid (H3BO3) is a boron compound that is soluble and circulates in plasma. It is a colorless, water-soluble, salt-like white powder, which have been used as pesticide since 1948. Normally, it is used to kill mites, insects, fungi and algae. For instances fleas, cockroaches, termites and wood decay fungi[8, 9]. Borate chemicals and boric acid have been used extensively for industrial purposes and its salts have been used for medication as an antiseptic to kill bacteria and fungi. Normally, it is used in the form of powder and liquid; depending to the target and conditions of pest, boric acid might applied as a spray or aerosol, as well as in the form of tablets, granule, pellets, paste or crystalline.