461 Occup Environ Med: first published as 10.1136/oem.2002.005686 on 16 April 2004. Downloaded from SHORT REPORT Cold blast furnace syndrome: a new source of toxic inhalation by nitrogen oxides I Tague, P Llewellin, K Burton, R Buchan, D H Yates ............................................................................................................................... Occup Environ Med 2004;61:461–463. doi: 10.1136/oem.2002.005686 precipitated by deep breathing. Fifteen to 30 minutes later, Aim: To describe a new toxic inhalation syndrome in blast several men developed shivers, a sensation of cold, and furnace workers. exertional dyspnoea. One man had a single episode of Methods: Fourteen workers developed acute respiratory haemoptysis. Symptoms took approximately one week to symptoms shortly after exposure to ‘‘air blast’’ from blast resolve. After the first incident, three men were sent to furnace tuyeres. These included chest tightness, dyspnoea, hospital (table 1). All recovered within two weeks, but one rigors, and diaphoresis. Chest radiographs showed pulmon- with pre-existing asthma developed an exacerbation. ary infiltrates, and lung function a restrictive abnormality. Symptoms were improved by oxygen and supportive mea- This report includes a description of clinical features of the sures. Further treatment was only required in one case (the affected workers and elucidation of the probable cause of the asthmatic). Workers in the later incidents were less severely outbreak. affected, possibly because of changes made to the process, Results: Clinical features and occupational hygiene measure- and did not require hospitalisation. ments suggested the most likely cause was inhalation of All workers were fit, only one having a history of previous nitrogen oxides at high pressure and temperature. While the respiratory disease. Interestingly, two of the workers could task could not be eliminated, engineering controls were recall having had identical symptoms eight years previously, implemented to control the hazard. No further cases have after unblocking tuyeres. This was confirmed in one case by an entry in the medical records, which reported that he had occurred. been ‘‘coughing and unable to take deep breaths’’. Several Conclusions: ‘‘Cold blast furnace syndrome’’ represents a workers had previously experienced zinc fume fever and previously undescribed hazard of blast furnace work, carbon monoxide poisoning, but said their symptoms were probably due to inhalation of nitrogen oxides. It should be different. considered in the differential diagnosis of acute toxic Chest radiographs in four men showed bilateral lower zone inhalational injuries in blast furnace workers. infiltrates suggestive of pulmonary oedema. Changes resolved within 24 hours. Lung function showed significant restriction, with improvement to baseline within one month. Repeat assessments one and two years later were within odern steel manufacture involves the use of a blast normal limits (except for pre-existing disease). http://oem.bmj.com/ furnace, where raw materials are reduced to molten iron and slag. Materials descend through a coke bed M OCCUPATIONAL HYGIENE MEASUREMENTS and are tapped at the base of the vessel. Hot, enriched ‘‘air Personal and stationary monitoring was conducted when blast’’ is injected through a series of tuyeres (air inlets) in the opening tuyeres. Inspirable and respirable dusts were base of the furnace, where reduction of iron oxide to molten analysed for iron, zinc, calcium, aluminium, cadmium, iron occurs. Occasionally, factors (for example, a power cut) arsenic, and vanadium using inductively coupled plasma may temporarily stop the supply of air blast, allowing cooling atomic emission spectrophotometry. Concentrations were on September 29, 2021 by guest. Protected copyright. of the iron and slag. This is referred to as a ‘‘cold furnace’’. In low or not detected. Respirable dust was analysed for quartz such circumstances, workers will plug most of the tuyeres with an infrared spectrometer, but low concentrations were with refractory material, then resume operation on the present. Benzene soluble fraction of total particulate matter remaining tuyeres to restore heat to the material entering (BSF), a measure of the fine particulate or fume, failed to the hearth. As the furnace heats up, workers will unblock the confirm significant hydrocarbons. Monitoring for hydrogen tuyeres without stopping the furnace. cyanide, sulphur dioxide, hydrogen sulphide, and carbon Unblocking tuyeres is a difficult job requiring at least monoxide using a GEM personal monitor showed levels well six men and personal protective equipment. A ‘‘gland’’ is below the Worksafe Australia standards.1 Monitoring for attached to the area delivering hot air to the tuyere, and a organic contaminants by gas chromatography showed low rock drill with a 3 m steel drill part is inserted through levels. the ‘‘gland’’ and forcefully pushed towards the opening of Results of initial monitoring thus did not identify the tuyere into the blast furnace. Because interruption of the likely cause. Careful consideration of clinical features function of the blast furnace is unusual, unblocking of suggested that symptoms might be due to exposure to tuyeres in a cold furnace is an uncommon, but periodic nitrogen oxides. Additional stationary monitoring was event. therefore undertaken to establish if these were present in the blast. Continuous sampling of the gas was conducted CASE DESCRIPTIONS through a device attached to the tuyere and passed through In three separate incidents of ‘‘cold furnace’’, 14 of a total of a cooling coil and pressure diverter into the analysing 18 workers exposed to blast furnace fumes during tuyere instrument. Sampling was performed during normal opera- unblocking noticed identical symptoms. Shortly after expo- tion of the blast furnace over a period of 43 minutes after a sure, they developed marked chest tightness and cough period when the wind volume was reduced. High peaks of www.occenvmed.com 462 Tague, Llewellin, Burton, et al Occup Environ Med: first published as 10.1136/oem.2002.005686 on 16 April 2004. Downloaded from Main messages Policy implications N ‘‘Cold blast furnace syndrome’’ results in acute N Occupational physicians should be aware of the dyspnoea, chest tightness, and pulmonary oedema. hazard regarding nitrogen oxides (NOx) in blast N This is probably due to exposure to nitrogen oxides furnace operations. (NOx), which may occur during the recovery process of N Occupational hygiene surveillance should include a ‘‘cold blast furnace’’. measurement of NOx. N Engineering controls may be required to minimise exposure to blast furnace gases. nitrogen oxides occurred directly after a stove change (73 and N Regular worker surveillance (including lung function) is 78 ppm), with the second peak when the wind volume was recommended. reduced. Nitrogen dioxide was not detected during the monitoring period. NO toxicity are incompletely understood, and clinical effects DISCUSSION may be difficult to separate from NO toxicity. Clutton-Brock This report identifies a previously undescribed hazard of work 2 reported a case of fatal pulmonary oedema in a 39 year old in blast furnaces, which we have called ‘‘cold blast furnace woman who died after exposure to NO from a contaminated syndrome’’. Inhalation of toxic fumes produced a highly x nitrous oxide cylinder during anaesthesia. The presumed characteristic syndrome in 14 of 18 workers. Given the 5 similarity of descriptions from affected workers employed in concentration was thought to be approximately 10 000 ppm. Inhaled NO is currently used in ICU settings in the range of different blast furnaces, the same agent is likely to have been 10 inhaled on each occasion. The differences in the severity of 10–20 ppm. the response between workers presumably reflect differences Although the samples were not collected in the breathing in dose produced by variations in proximity to the blast, zone of workers and hence cannot be directly compared to differing process conditions, individual variations in respira- occupational exposure standards, stationary sampling con- tory rate and respiratory protection, and ongoing attempted firmed high concentrations of nitrogen oxides were present engineering solutions. in the tuyere gas, at 73 and 78 ppm. Following the incidents, ‘‘Air blast’’ from the furnace is a complex mixture of the ‘‘gland’’ was altered, and the standard operating proce- different gases containing carbon monoxide, sulphur dioxide, dure for opening tuyeres revised. On several subsequent ozone, and heavy metals. Sampling showed that none of occasions the procedure has been repeated without incident. these were above exposure standards, so another agent was Toxic inhalation of nitrogen oxides fits most closely with presumed responsible. the clinical picture and occupational hygiene measurements, It seemed likely that levels of the toxic agent inhaled were and seems the likeliest cause of the syndrome observed. We high, in view of the systemic symptoms experienced by the have named this ‘‘cold blast furnace syndrome’’. To date, all workers. It was likely that the toxic agent(s) was relatively workers have made a full recovery, but the long term water insoluble, as soluble agents tend to provoke irritation consequences of ‘‘cold blast furnace syndrome’’ are difficult and inflammation of the proximal respiratory mucosa, and in to predict. In the literature, acute inhalational exposures to these cases