Urea – inhalable fraction. Documentation of proposed values of occupational exposure limits (OELs)

Abstract

Urea is a non-flammable, colorless or white crystalline solid. It has a faint aroma of ammonia and a cooling, saline taste. It is hygroscopic, very well soluble in water. During long-term storage and in aqueous solutions urea partly decomposes with the release of ammonia and carbon dioxide. Urea is used as a: component of fertilizer and animal feed; raw material for production of plastics, flame-proofing agents, adhesives, medicines, cosmetics and household products; reductant in selective catalytic reduction (SCR) systems used to reduce NOx emissions from stationary and mobile sources; deicing compound on roads, railroad tracks and airport runways; in the food industry as an additive for bakery products, alcoholic beverages and gelatine-based products and as a reagent in laboratories. In 2012, world production of urea was estimated to be around 184 million tonnes and is projected to increase further. In the European Chemicals Agency, urea was registered by 5 companies from Poland. The number of workers exposed to urea in 2 of these plants is a total of 201 people. Urea is an endogenous product, formed in the liver in the urea cycle from ammonia formed by the catabolism of amino acids and proteins, is then excreted by the kidneys. An adult man excretes about 20 ÷ 35 g of urea in the urine during the day. Most of the information on the effects of urea in humans comes from patients with renal insufficiency who have elevated urea levels. Adverse effects of urea include: headache, nausea, vomiting, syncope, confusion, electrolyte abnormalities in the blood. Urea has a slight irritating effect on the eyes and does not irritate the skin. At concentrations above 10% urea has a keratolytic effect - it facilitates peeling and increases the permeability of the stratum corneum, thereby increasing the therapeutic activity of many topical medications. Based on animal studies urea has low acute and chronic toxicity and no carcinogenic or reproductive toxicity. Urea does not meet the classification criteria as a CLP hazardous substance. Due to very low vapor pressure, exposure is possible only to urea dust. Therefore, in order to protect workers from the nuisance of particulate matter (dust) of urea, the MAC (TWA) value of 10 mg/m3 was recommended as for other dusts not classified for toxicity but posing a hazard for visibility reasons. There is no basis for determining the short-term exposure limit value (STEL) and the biological exposure index value (BEI).