As a trade, food processing is tremendously diverse. Ranging from agriculture and fishing, to slaughtering and raw processing of foods to refined processing and cooking, the numerous and varied jobs offer countless types of potentially hazardous exposures. Exposure to airborne particles of organic material is the cause of a diversity of clinical conditions in all of the jobs within the group. Comprehensive reviews on the specific diseases related to farming are found in Linaker and Smedley [1] and in Schenker et al. [2]. Excellent reviews also exist in relation to bakery and seafood workers and to several of the other jobs within these trades. The history of disease related to crop, soil and animal contact is the oldest in the history of man’s occupational exposures. Descriptions of respiratory problems arising from such contact can be found in several ancient texts, many of which describe symptoms of readily recognizable conditions such as pneumonitis or chronic bronchitis, whereas asthma and rhinitis – the two respiratory conditions most widely associated with farming today – are less easily recognized. We do not know whether or not allergic reactions were less common in man’s long history of farming than they are today. Certainly this question has attracted much recent attention in relation to the ‘hygiene hypothesis’.

A 65-year-old nonsmoking dairy farmer was brought to the hospital in respiratory distress. He had a high fever, inspiratory crackles and bilateral lung infiltrates. No detailed history was possible as the patient was intubated and mechanically ventilated with supplemental oxygen. He was given broad spectrum intravenous antibiotics. His condition rapidly improved and he was weaned off the respirator within 2 days and released from the hospital within 5 days of admission to continue oral antibiotics. Final diagnosis was bilateral pneumonia (no pathogens had been identified). The patient returned to the hospital a week later complaining of shortness of breath and chills. At this time a complete history revealed that he was a dairy farmer who had recently been using poorly conserved hay as bedding for his cows. The hay was so poor that he had used a chain saw to cut the bales into sections. The diagnosis of farmer’s lung was confirmed by serology, CT scan and BAL. His recovery was complete and, by changing his work environment, he was able to continue farming without recurrence.

Care must be taken to differentiate farmer’s lung from an infectious process or inhalation fever such as ODTS. ODTS also occurs in dairy farmers but in this case the exposure to moldy bioaerosols is massive, e.g. when decapping a haylage silo. The response is limited to the airways but extends to the alveoli. It is caused by toxic material in the dust. ODTS is also called toxic pneumonitits and has previously been called mycotoxicosis. The latter name was changed when it became evident that the toxic material which causes it is most likely also derived from bacteria (e.g. endotoxins). This self-limiting syndrome is not an immune-mediated disease. As for farmer’s lung, the diagnosis of ODTS can usually be made simply by careful questioning and by remembering this possibility. There are no standardized diagnostic criteria; the diagnosis is only made by history and follow-up and by ruling out other diagnoses such as an infectious process and farmer’s lung. The dyspnoea, fever, cough and malaise appearing a few hours after exposure resemble HP but symptoms resolve spontaneously within 1-2 days. It is likely that more than one agent can give rise to the syndrome and that some of the mixes of agents present, e.g. in animal houses and stables, are more potent than single agents.

A 42-year-old corn producer came to the hospital emergency room complaining of severe cough and chills since the evening before. His cough was unrelenting but he produced very little, blood-tinged sputum. Awaiting his turn to see the physician the receiving nurse obtained his vital signs. He had a fever of 39 C, his pulse was regular at a frequency of 140 beats/minute and his blood pressure was 140/94. A chest radiograph and spirometry were obtained, both of which were normal. Upon questioning the patient reported that he had been cleaning one of his corn silos the day before. He had spent 2 hours cleaning moldy grains of corn that remained on the edges of the otherwise empty silo. The doctor suspected an acute infectious bronchitis and was about to prescribe an antibiotic when the patient reported prior similar, although less severe, episodes after cleaning his silos in the past. With this additional information the doctor prescribed a cough suppression agent and aspirin. The patient was told he probably had ODTS and asked to return if the symptoms had not cleared within 24 hours. His recovery was uneventful, confirming that the diagnosis had probably been correct.

A common disease entity among farmers is the ‘asthma-like syndrome’ with reported prevalences in some European farming populations of 20-50%. The syndrome resembles asthma as it can present with chest tightness, wheeze and dyspnea. Allergic reactions are absent. In contrast to the common worsening of asthma during a work week, the symptoms of asthma-like disease tend to improve as the working week progresses. Some allergic asthma may, occasionally, show the same pattern or in contrast may be worse on Saturdays after an entire week at work. In farming, such temporal patterns are usually very difficult to establish because work is rarely performed only on weekdays. Any episodic or persisting respiratory symptoms without systematic involvement are therefore evocative of asthma or asthma-like disease. Grain dust, ammonia and endotoxins have all been implicated in asthma-like disease – all of these exposures being common in animal houses. Endotoxins, ubiquitously present everywhere on farms and stemming from bacterial growth on feed, plant debris, in animal houses and elsewhere, have been associated not only with ODTS but also with worsening of asthma. Endotoxins are also commonly suspected of being at least partly responsible for asthma-like syndromes.

In a current or former farm worker or farmer presenting with a history of persistent or recurring productive cough and dyspnoea, chronic bronchitis is not unlikely even in a nonsmoker. In nonsmoking farmers and workers in animal confinement buildings, chronic obstructive pulmonary disease (COPD) has been found in 17%, with 3% having severe disease. COPD appears to be more common in older farmers than in comparable nonfarming populations. Several agents within the farming environment can reach and cause inflammation of the conductive airways: they include organic and inorganic dust, gases and fumes. Alone none of these has been convincingly demonstrated as a sufficient cause of COPD, but endotoxin in animal confinement buildings has repeatedly been associated with accelerated loss of lung function and with COPD. An increased risk of chronic bronchitis has also been found among farmers who have experienced ODTS. In dry climates an association of chronic bronchitis with dust exposure has been put forward. Furthermore, exposures to welding fumes, exhaust and smoke from fires are not uncommon among farm workers and may add to the risk of chronic bronchitis. Thus, whether the presenting symptoms are wheeze, dyspnoea, cough, chest tightness, or are less specific, any farmer reporting historic episodes of respiratory problems may well have some degree of COPD.

A farmer presenting with pulmonary fibrosis should be questioned about excessive exposure to dust from sand or soil or to the herbicide paraquat. Such inhalatory exposures are not uncommon during field work, but also occur when processing sugar beets, potatoes and grain or when burning straw etc., and can lead to fibrosis – an important diagnosis to consider in the dyspneic farmer.

Irritants like ammonia or other gases, cleaning agents, or other chemicals are regularly handled on farms. Accidental high exposure to many such irritants can cause RADS. RADS is not easily missed due to the new onset of asthma-like symptoms very shortly after unusual episodes of exposures. It is debated how long RADS can persist. Distinguishing between whether persisting symptoms represent an underlying asthma or if one should accept an entity called persisting RADS may be purely academic since both diseases may be caused by exposures at farms (and other workplaces with chemical irritants) and require anti-asthmatic treatment. At lower concentrations, gases from decomposing organic material can become concentrated in silos and cause respiratory irritation. Usually a self-limiting condition, such an inflammatory reaction of the airways to high concentrations of noxious gases can turn into life-threatening lung oedema or cause a long-lasting RADS. Suffocation or near death is not uncommon in such silos or in manure pits or other enclosed or low-level spaces that may fill with hydrogen sulfide.

Zoonoses are considered a rare cause of respiratory morbidity in farmers. Psittacosis, which is seen among poultry farmers due to their contact with infected birds, usually presents with nonproductive cough and other symptoms of a respiratory tract infection. Fever and other systemic symptoms will also be present. Bovine tuberculosis is well controlled in Europe and North America and infection of farmers has become rare. In some developing countries primary tuberculosis due to contact with cattle infected with Mycobacterium bovis remains a serious health problem. Fever may also be a symptom of Coxiella burnetii infection (Q fever) or other rare infectious diseases. Little is known about the prevalence of mild flu or cold-like viral infections transmitted from swine or other livestock. Such zoonoses may have become more prevalent because of higher density of animals in confinement buildings and because farm workers spend longer working hours inside these buildings. Farm workers, farmers and their relatives may if they present with airway infections or otitis, have been infected with multiresistant Staphylococcus aureus (MRSA), possibly transmitted from pigs. Such cases have been documented in recent years and are probably due to the frequent use of antibiotics not only for animal treatment but also as growth enhancers in most countries.