Nitrogen dioxide (NO₂) is a gas commonly present in both occupational and general environments. It is a product of fired materials containing nitrogen. In 2001 in Poland 736 workers were exposed to NO₂ at a level above the MAC value. Respiratory tract is a critical organ for toxic action of NO2 in both humans and animals. This chemical is a clastogen. In the industry pneumotoxic effects in workers exposed to NO₂ at level of 0.8 – 5.1 mg/m³ were observed. The MAC (TWA) value of 0.7 mg/m³ was calculated on the basis of the LOAEL value (2.95 mg/m³) and relevant uncertainty factors. The MAC (STEL) value was established by calculation at level of 1.5 mg/m³.

Isophorone diisocyanate (IDPI) is a colorless or pale-yellow liquid. IDPI has yielded highly stable polyurethanes that have been exceptionally resistant to light discoloration or chemical degradation. Other possible uses are paints and varnishes formation, as well as casting compounds and mastics to use in highly flexible textile coatings. IDPI is irritant to the skin and eye. In experiment on mice RD₅₀ for IPDI was 2 mg/m³. In workers it was observed the cross-sensitivity between IDPI and other isocyanates. In 4-weeks inhalation exposure the observed effect of IDPI exposure was irritation of pulmonary system; NOAEL = 0.64 mg/m³. According to the irritant and sensitization effect of IDPI, the MAC-STEL of 0.04 mg/m³ and the irritation (I) and sensitization (A) notations are recommended.

Methyl isocyanate is a clear, flammable liquid with a strong odor. Methyl isocyanate is used in the preparation of carbamate insectides, polyurethanes, polymers and some pharmaceuticals. Methyl isocyanate is a skin, ocular, and respiratory tract irritant. The RD₅₀ (respiratory dose 50) value in mice is 3.1 mg/m³. In a 10-day inhalation study on rats the concentration 1.4 mg/m³ was identified as the no-observed-adverse-effect level (NOAEL). Based on this data the Expert Group for Chemical Agents has established an 8-hour MAC (TWA) value of 11 mg/m³. This value is intended to minimize the potential for reported eye, upper respiratory tract and skin irritation.

Diesel exhaust contains components of complete combustion such as nitrogen, carbon dioxide and of incomplete combustion such as nitrogen oxides, carbon, monoxide, hydrocarbons, aldehydes, phenols, sulfur compounds, which can cause irritation of the upper respiratory track. Diesel exhaust also produces submicron-sized particles that cause soiling and poor visibility. These particles have been regarded as presenting only a minimal health risk; however, the presence of carcinogens adsorbed on the particles has raised concerns about the potential for lung cancer from exposure to diesel exhaust. Therefore, to establish MAC values for diesel exhaust data from studies on carcinogenic effects in laboratory animals were considered. A linear model was used in considering assessment of the risk for the worker population. Based on acceptable risk 10^-3 MAC value for diesel exhaust was calculated to be 0.5 mg/m³. No MAC-STEL values have been established.

Nitrous oxide (N₂O) is a gas mainly used in medicine, dentistry, and veterinary medicine as an anaesthetic. Medical staff is a subpopulation exposed to this chemical. Nitrous oxide exerts neurotoxic, embriotoxic, fetotoxic, and teratogenic effects on human and animal organisms. This compound is an inhibitor of methionine synthase. The MAC (TWA) value of 90 mg/m³ was calculated on the basis of the LOAEL value (180 mg/m³) for neurotoxic effect in humans. The MAC (STEL) value has not been established. Moreover Ft (fetotoxicity) notation is recommended.

Hydroxypropyl acrylate (HPA) is a mixture of isomers: 2-hydroxypropyl acrylate and 2-hydroxy-1-methylethyl acrylate. HPA has been used in the manufacture of thermosetting resins for surface coatings. HPA is of moderate to low toxicity after oral intubation. The rat oral LD₅₀ was 250 to 500 mg/kg with reports of values as high as 590 to 1300 mg/kg. Rats inhaling saturated HPA vapor generated at room temperature for 7 to 8 hours survived. Marked signs of eye, nasal, and respiratory irritation were noted during the exposure period. When dogs were repeatedly exposed by inhalation at 28 mg/m³ 6 hours/day, 5 days/week for a total of 20 or 21 days during a 1-month period, signs of ocular, nasal, and respiratory tract irritation were observed. Rabbits and rats exposed to HPA under an identical protocol developed signs of nasal, respiratory, and ocular irritation. As for dogs, there was no adverse effect on body weight, hematological, clinical chemistry, or urinalysis parameters. A no-effect level for repeated inhalation exposure to HPA was calculated below 28 mg/m³. The material causes moderate burns (even when contacted as a 10% aqueous solution). These materials are of variable sensitization potential. Several publications have described contact allergy in exposed workers. Based on the signs of ocular, nasal and upper respiratory tract irritation documented in animals after repeated HPA inhalation, an 8-h TWA value of 2.8 mg/m³ is recommended. In order to minimize irritation symptoms, STEL of 6 mg/m³ is recommended. The notation of “C” – corrosive – and the skin notation are assigned (DL50s < 1000 mg/kg). HPA can be regarded as a skin sensitizer, hence, a sensitizer, “A”, notation is assigned.

Alphamethrin (alpha-cypermethrin) is a synthetic pyretroid applied as an insecticide. It is produced from cis-2,2 dimethyl-3-(2’2’dichlorovinyl) cyclo-propanocarboxyl acid, 3-phenoxybenzoaldehyde and sodium cyanide. The-re are several forms of this preparation available for use (CS – capsule suspension designed for dilution in water, EC – concentrate to make an aqueous emulsion, ULC – ultra low volume liquid ready to use). Annual production in Poland is about 100,000 l of 10% concentration. Direct exposure to alphamethrin may result in skin and/or mucosa irritation, reddening and swelling. No case of poisoning has been reported. Intragastric administration of alphamethrin to rodents demonstrates moderately high toxicity dependent on the concentration of the preparation and on the carrier. The following clinical symptoms typical for pyretroids are observed in the case of acute intragastric exposure: disturbed coordination of movements, dyssynergia, chorea, abnormal gait and tip-toe walk. Increased salivation and lacrimation, ruffled fur, tremor and clonic convulsions are also characteristic. In the majority of cases ani-mals died within the first 3 h, those who survived recovered within 7 days. The dermal toxicity of the preparation is low and clinical symptoms depend on the preparation form. No clinical alterations were seen in rats after exposure to pour-on preparations. SC preparation caused hematomas round the animals’ nose and eyes. After EC or ULV application lacrimation, ruffled fur, aggression and diarrhea were observed. In rabbits, undiluted alphamethrin spreaded on uninjured and depilated skin resulted in minimal irritation. All forms of the preparation for use did not demonstrate irritating activity or were only mildly irritating. In the Draeize test carried out on rabbits, alphamethrin preparations caused eye irritation, corneal opacification, iris injury. Alphamethrin does not demostrate skin sensitization in guinea pigs. In tests with Salmonella typhimurium and Saccharomyces cerevisiae, both with and without metabolic activation alphamethrin was detected not to be mutagenic. Negative results were also obtained in in vitro studies performed with chromosomes and DNA from rat bone marrow and liver cells. There are no available literature data on alphamethrin cancerogenic, embryotoxic or teratogenic activity nor on its effect on reproduction. Alphamethrin is weakly absorbed by the alimentary tract, respiratory tract and the skin. Due to its lipophil properties, in higher concentration alphamethrin accumulates in fatty tissue, in the skin, liver, kidneys, adrenal glands and ovaries. In humans, the rate of excretion depends on the dose – about 43% of the dose is eliminated with urine within the first 24 h in the form of free or conjugated cis-cyclopropanocarboxyl (cis-CPA) acid. Elimination with urine does not increase after administration of another dose. On the basis of the results of long-term exposure of dogs, the NOAEL value was accepted to be 90 mg of alphamethrin/kg of fodder (equivalent of about 2.25 mg/kg b.w./24 h). It was converted to a dose of absorption by humans during 8 h exposure and MAC value was calculated with the application of three coefficients of uncertainty. The MAC value of 1 mg/m³ was suggested.

Benzothiazole is a yellow liquid with an unpleasant odor similar to quinoline. Benzothiazole is used as a chemical intermediate in organic synthesis. It is a precursor of rubber accelerators and a component of cyanine dyes. It is also used as a flavoring substance in foods and as an antimicrobial agent. Occupational exposure to benzothiazole through inhalation or dermal contact occurs mostly at rubber processing facilities and during asphalt paving. Benzothiazole is harmful substance in laboratory animals in acute toxicity testing. It exerts systemic action on the central nervous system and the liver. In the available literature no data on the toxicity in humans, or genotoxicity, carcinogenicity, fetotoxicity, and teratogenicity of benzothiazole in laboratory animals have been found. In setting exposure limits, the results of an acute toxicity testing were considered. Based on the LOAEL value obtained in an experimental study (135 mg/kg) and the relevant uncertainty factors, a MAC (TWA) value has been calculated at 20 mg/m³. With regard to systemic effects of benzothiazole no STEL value has been established. Because benzothiazole has been shown to penetrate the skin in amounts sufficient to induce systemic toxicity, a skin notation (Sk) is considered appropriate.