Alone in the rubber industry more than 350,000 workers are employed in the EU; additionally about 260,000 workers are estimated to be exposed to metal-working fluids and corrosion inhibitors. N-nitrosamines are typically not intentionally produced but usually formed from secondary amines and nitrosating agents under certain reaction conditions. Typical workplaces where N-nitrosamines can occur are in the rubber, leather, metalworking and chemical industry. Inhalation and dermal exposure are the main routes of exposure for nitrosamines. Many N-nitrosamines are classified according to CLP as Carcinogenic Category 1A, 1B or 2. Epidemiological data indicates that exposure to nitrosamines both in occupational settings and in general population may be associated with a cancer risk of various types.

Where risks occur

Exposure to N-nitrosamines may occur in the rubber industry during tasks like weighing, mixing, semi-finished product processing, vulcanization and post-treatment. Rubber products may be potential sources for nitrosamines as well. Exposure has been reported to occur in the metalworking industry if metal working fluids contain high nitrate/nitrite levels. Typical tasks are maintaining and servicing machines, manual handling of machine tools with the close presence of an operator and the likelihood of spraying, splashing or evaporation of the metal working fluids and mixtures during operation. It is, however, not known whether these conditions apply in Europe anymore. Production and use of amines in the chemical industry, as well as decanting and filling operations of amines and their use in further chemical processes e.g. coatings by the coagulation process, production of polyacrylonitrile fibres, are workplaces where N-nitrosamines can occur. In the past, further affected workplaces could also be found in the leather industry, in electronic industry and in foundries.

More about the substance

N-nitrosamines are neither produced nor used. N-nitrosamines are usually generated from secondary amines in contact with other nitrogenous compounds and nitrosating agents. Nitrosating agents are nitrous acid and its salts, the nitrites, nitrogen oxides from engine exhaust or organic nitro and nitroso compounds. Secondary amines can be present in chemical additives or as ingredients from ready-to-use products. Well-known secondary amines with the potential to generate N-nitrosamines are e. g. diethylamine, diethanolamine, diethylpropylamine, morpholine, pyrrolidine. Secondary amines can also be formed from other nitrogen-containing compounds in relevant amounts, e. g. by hydrolysis, thermic or biogenic decomposition. Typical secondary amines can also be found among corrosion inhibitors, vulcanisation accelerators, solvents and water-miscible or water-mixed cooling lubricants like metalworking fluids.

Hazards that may occur

Exposure to N-nitrosamines has been linked to a wide variety of cancer types, e.g. development of cancer in the bladder, stomach, esophagus, prostate, pancreas and liver leukemia and multiple myeloma.

The latency period between exposure and cancer development has been estimated to be 15 years.

What you can do

In first line, measures are elimination and prevention of the risks. Replace secondary amines with suitable substitutes for your specific application, e.g. primary or tertiary amines and alkanolamines. A few secondary amines are known, which do not form carcinogenic N-nitrosamines, e.g. dicyclohexylamine. There are different alternative chemical systems available for applications of secondary amines, e.g. in the rubber industry. To reduce the risk of N-nitrosamine formation, keep nitrosating agents or precursors like nitrite away and the concentration of secondary amines low. If necessary, apply inhibitors for N-nitrosamine formation, such as ascorbinic acid, sulfamates, p-aminobenzoic acid, alpha-tocopherol, primary amines and primary alkanolamines. Check or monitor the maximum concentration of secondary amines, nitrosating agents or the pH-value in products. Comply to national use restrictions, if present. If substitution is not possible, implement regular exposure assessment to check if your protective measures in place are effective or whether further actions need to be taken. Technical protective measures like closed systems or exhaust of process-related N-nitrosamines are the alternative if substitution is not applicable. Make workers continuously aware of the effects of exposure. In addition, train workers on hazards, safe work practices and on effective hygiene measures. Ensure that workers have adequate personal protective equipment, such as protective clothing and gloves, if necessary. Personal protective equipment should only be used as a last resort, after the possible technical solutions have been presented.

References: AGS, ECHA, FIOH, DGUV, HSE, BAuA, Statista