Silicosis and Occupational Asthma: Symptoms, Diagnosis, and Control

Posted on Nov 15, 2024 in Biology

Silicosis

Definition

Silicosis is a disease caused by inhaling free silica (SiO2). It’s characterized by disseminated nodular fibrosis, diagnosed through radiological examination. Silicosis leads to impaired lung function, especially in advanced stages.

Causes and Sources of Exposure

Agents: Free crystalline silica or silicon dioxide (SiO2). Note: This differs from total silica, where silicon bonds with other elements as silicates.

Sources: Various forms of SiO2 exist in rocks (e.g., granite), pure quartz, minerals, sand, and fossil deposits. Extraction, milling, and landslides generate large amounts of silica dust.

  • Mining: Drilling, transporting, crushing, and grinding metal ores (copper, iron) and non-metallic ores (nitrate, coal). Extraction and industrialization (milling and sieving) of quartz and calcite for cement production.
  • Laboratory Analysis: Handling mineral samples.
  • Metallurgy: Iron ore processing (iron and steel), non-ferrous metal processing (copper), converter operations, casting molds, abrasive cleaning, and grinding.
  • Sandblasting: Cleaning castings, steel structures, and ship hulls.
  • Manufacturing: Refractory bricks, silica glass tiles, ceramics, earthenware, mixing, cutting, polishing, sanding, grinding, and industrial abrasive use.

Diagnosis

Occupational History: Evaluate exposure risks, characteristics, and previous/current work exposure. Document personal and environmental protection measures.

Clinical Presentation: Often asymptomatic initially. Late-onset symptoms include cough, expectoration, backache, and dyspnea (shortness of breath), which may become permanent.

Radiology: Pulmonary nodules are key indicators. Size and number of opacities/nodules help define the diagnosis.

Pulmonary Function Tests: Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory volume percent (FEV%), and maximum mid-expiratory flow (MMEF) assess lung function.

Medical Surveillance and Environmental Monitoring

Medical Surveillance: Pre-employment radiological and functional exams, along with a history of previous work and tuberculosis risk. Regular reviews based on exposure intensity.

Environmental Monitoring: Regular evaluation (1-2 times/year) using environmental indices. Dust levels must stay below permissible exposure limits (PELs).

Control Measures

Environmental: Dust control principles vary by operation and include:

  • Agent replacement
  • Process enclosure
  • Ventilation (general and local exhaust)
  • Powder wetting

Personal: Use appropriate respirators for specific dust types and ensure proper maintenance (filter changes).

Occupational Asthma

Occupational asthma involves reversible airway obstruction, often occurring in episodes, linked to a workplace agent. Symptoms can manifest immediately after exposure or several hours later, making diagnosis challenging.

Sources and Routes of Exposure

Sources: Multiple specific work activities and adjacent areas with described agents.

Routes of Entry: Primarily through the airways. Oral exposure may cause symptoms, but typically not respiratory issues.

Control

Environmental: Ventilation systems can reduce risks, but may be insufficient for sensitized individuals. Identifying specific agents allows for task modification, product substitution, or personal protective equipment (PPE).

Personal: Removing the occupational risk is crucial.

Pathology and Diagnosis

Pathology: At least two mechanisms are involved: chemical irritation and hypersensitivity reactions.

Environmental Indices: No safe exposure level exists for sensitized individuals. Reactions can occur at any concentration.

Diagnosis:

  • Occupational History: Intermittent obstructive bronchial episodes linked to specific work activities.
  • Radiology: Usually no radiological findings unless associated with hypersensitivity pneumonitis.
  • Functional Study: Reduced dynamic airflow.

Pesticides

Pesticides are organic or inorganic, natural or synthetic chemicals used to control organisms harmful to humans, plants, and animals. Exposure can cause severe or acute poisoning through dermal, respiratory, or oral routes.

Chemical Composition Categories:

  • Phosphorus (e.g., Parathion, Diazinon, Malathion)
  • Chlorinated (e.g., DDT, Chlordane, Dieldrin)
  • Organic thiocyanates (SNC group)
  • Carbamates (e.g., Sevin, Isola, Pirela)
  • Dinitro derivatives (e.g., 4,6-Dinitroorthocresol)
  • Carbamic esters (e.g., Thiram, Ferbam, Zineb)
  • Inorganic (e.g., SO2, CuSO4, HgCl2, As2O3)