Chemical Hazards - Page 4 of 8

HEALTH EFFECTS OF SPECIFIC BODY SYSTEMS

Depending on their physical characteristics, certain chemicals have an affinity for specific target organs or body systems (Figure 2). Once deposited, they cause impaired functioning of the normal metabolic processes, which if permanent, ultimately results in disease.

Biological effect monitoring is able to detect some of these early sub-clinical biochemical changes, while medical surveillance programmes are designed to detect early adverse health effects due to exposure to a particular chemical substance before they become clinically apparent (Table 1, below and Figure 1).

Table 1. Relationship between environmental monitoring, biological monitoring, biological effect monitoring, medical surveillance and clinical diagnosis
Procedure	Definition	Example
Environmental monitoring	Measures the airborne concentration of the chemical in the workplace environment	- lead fumes - mercury vapour
Biological monitoring	Measures the extent of absorption of the chemical by the worker by determining the concentration of the substance and its metabolites in human tissue or fluids (e.g. blood, urine, adipose tissue)	- blood lead - urinary arsenic
Biological effect monitoring	Measures early physiological/ biochemical effects of exposure on the human body, which are reversible on removal from exposure	- zinc protoporphyrin - red cell cholinesterase
Medical surveillance	Aims to identify workers with early adverse health effects, which are likely to be reversible or do not progress to significant functional impairment when exposure conditions are improved	- serum creatinine, urea - serum transaminases - skin prick tests - neurobehavioural tests
Clinical diagnosis	Identifies workers with clinical signs and symptoms of an occupational disease with significant functional impairment, which is commonly irreversible despite improvements in exposure conditions	- clinical assessment accompanied by confirmatory diagnostic tests e.g. tissue biopsy

This impaired functioning progresses to a clinically diseased state and manifests in the individual worker as symptoms and signs referable to the specific target organ affected. Some chemical substances exert their toxic effect on a specific target organ, usually locally at the site of entry. Other chemicals exert their effects systemically (more than one organ system distant to the site of entry). With mixed exposures, individual substances can act through similar toxicological mechanisms so that the effects reinforce one another and their effects can be additive. In some instances the overall effect is considerably greater than the sum of individual effects and the system is synergistic. Table 2 indicates the most common organs affected, the symptoms associated with abnormal function and the tests commonly used in medical surveillance.

Table 2. Adverse health effects associated with exposure to hazardous chemical substances according to target organ system and appropriate tests used in medical surveillance
Target organ system	Examples of hazardous chemicals	Health effects	Symptoms of impaired function	Medical surveillance tests
Blood and blood forming organs	-chemical asphyxiant gases (cyanide, carbon monoxide, hydrogen sulphide, nitrogen dioxide) - arsine, cyanide- benzene, lead	- asphyxiation due to tissue hypoxia or chemical-specific response - bone marrow dysfunction (anaemia, low platelets) - intravascular haemolysis - leukaemia	- asymptomatic - jaundice, dark urine - abdominal pain and swelling	- full blood count - zinc protoporphyrin* (ZPP)
Nervous system	-chemical asphyxiant gases (cyanide, carbon monoxide, hydrogen sulphide, nitrogen dioxide) - lead, manganese, mercury - solvents (hexane; trichlorethylene)	- encephalopathy - cognitive effects (memory, concentration, speech) - mood and personality effects - peripheral neuropathy (sensory/motor effects)	- headache, drowsiness - vision/hearing loss - loss of memory, concentration - abnormal limb sensation and movements - mood and personality changes	- visual fields - audiometry - nerve conduction tests* - neurobehavioural test battery*
Liver	- solvents (toluene, trichlorethylene, xylene, dinitrobenzene) - ethanol - arsenic	- hepatitis, cirrhosis, cancer - production of toxic chemical metabolites	- jaundice, dark urine - abdominal pain and swelling	- liver function tests (transaminases: ALT, AST, Gamma-glutamyl transpeptidase: GGT)
Kidneys and bladder	- lead, cadmium, mercury, platinum, chromium, arsenic - solvent mixtures, trichlorethylene – amines	- glomerulonephritis - tubular necrosis - cancer	- increased or decreased urine output - dark urine	- proteinuria - serum urea, creatinine, uric acid - urine cytology
Reproductive system	- lead, cadmium, methylmercury, toluene	- infertility - miscarriages - foetal birth defects	- inability to conceive	- semen analysis* - hormonal analysis*
Skin	- oils, acids, alkalis, solvents - cement - nickel, mercury, chrome, arsenic	- contact allergic and irritant dermatitis - skin burns, ulcers - cancer	- red, swollen, itchy, scaly, crusty skin - skin burns, ulcers	- skin patch tests*
Respiratory system	- chlorine, sulphur dioxide, ammonia - chrome, nickel, platinum salts - oxides of nitrogen - metal fumes - asbestos, silica, coal	- respiratory tract irritation - occupational asthma - hypersenstitivity pneumonitis - chronic obstructive lung disease - pneumoconiosis- cancer, mesothelioma	- nasal perforations, ulcers, bleeding - wheezing, shortness of breath, tightness - cough - excessive phlegm production	- chest radiography -spirometry - skin prick tests - serum antibodies (RASTs) - non-specific challenge tests*

* Specialised expertise required