Environmental & Occupational Health

Introduction: Environment and Health

Environmental health encompasses the assessment and control of those environmental factors that can potentially affect health. It includes air quality, water and food safety, chemical exposures, radiation, noise, and the built environment. Occupational health focuses specifically on the health of workers and the hazards of the workplace. Climate change is now recognised as the defining environmental health challenge of the 21st century.

Air Quality and Respiratory Health

Outdoor air pollution: the WHO estimates that ambient (outdoor) air pollution causes approximately 4.2 million premature deaths globally per year. Key pollutants:

• PM2.5 (fine particulate matter, diameter < 2.5 μm): the most harmful air pollutant. Penetrates deep into the alveoli; associated with cardiovascular disease (increased MI, stroke), COPD exacerbations, lung cancer, and adverse pregnancy outcomes. Sources: vehicle exhaust, industry, wood burning. The WHO 2021 guideline is annual mean PM2.5 ≤ 5 μg/m³ (revised down from 10 μg/m³).

• NO₂ (nitrogen dioxide): produced by combustion (vehicles, power plants). Causes airway inflammation; exacerbates asthma; impairs respiratory defence. Most New Zealanders' outdoor NO₂ exposure is below WHO guidelines.

• Ground-level ozone (O₃): formed by photochemical reactions of VOCs and NOx in sunlight. A respiratory irritant causing bronchoconstriction, especially in asthma and COPD.

Indoor air pollution: a major health issue globally — 3.2 million deaths/year from household solid fuel combustion (wood, charcoal, dung). In NZ: indoor air quality concerns include wood-burning fires (PM2.5), secondhand tobacco smoke, mould and dampness (respiratory disease in children — disproportionately affects Māori/Pacific in substandard housing), and radon (from granite bedrock, increasing lung cancer risk).

NZ-specific air quality: cities with significant PM2.5 problems include Christchurch (winter wood-burning season), Nelson, and Timaru. The National Environmental Standards for Air Quality (NES-AQ) set legal limits. Airshed management restricts wood-burning in high-pollution areas.

Water Safety

Safe water: the WHO defines safe water as free from harmful biological, chemical, and physical agents. Access to safe water is SDG 6 and a basic human right. Waterborne disease remains a major global burden (~1.5 million diarrhoeal deaths/year, predominantly children in LMICs from faecal-oral contamination).

Microbiological hazards: Cryptosporidium, Giardia, Campylobacter, Salmonella, E. coli O157:H7. The 2016 Havelock North campylobacter outbreak — New Zealand's most significant drinking water contamination event — infected approximately 5,500 people (from a population of ~14,000), killed 4, and left dozens with ongoing illness. The source was sheep faeces contaminating the Brookvale bore water supply, exacerbated by inadequate disinfection.

Chemical hazards: lead (lead service pipes — a historical NZ issue in older homes), nitrates (agricultural runoff into groundwater — "blue baby syndrome" — methaemoglobinaemia in formula-fed infants), arsenic (geothermal areas), and fluoride (used at low doses in water fluoridation to prevent dental caries — approximately 54% of NZ water supplies are fluoridated; the Health (Fluoridation of Drinking Water) Amendment Act 2021 empowers the Director-General of Health to direct water suppliers to fluoridate).

NZ drinking water regulation: the Water Services Act 2021 and Taumata Arowai (the Water Services Regulator, established 2021) replaced the fragmented system of local authority self-regulation following the Havelock North inquiry recommendations.

Occupational Health

Occupational hazards are classified into four categories:

1. Physical hazards: noise (industrial deafness is the most common occupational disease in NZ — ACC receives thousands of claims annually), vibration (hand-arm vibration syndrome in chainsaw/drill users), extreme temperatures, ionising radiation (X-ray workers, uranium mining), non-ionising radiation (UV from sun exposure — skin cancer risk for outdoor workers).

2. Chemical hazards: solvents (neurotoxic), heavy metals (lead, mercury, cadmium — cumulative toxicity), asbestos (mesothelioma, asbestosis — responsible for ~170 deaths/year in NZ, predominantly tradespeople exposed pre-1980), pesticides (organophosphate neurotoxicity), silica dust (silicosis — engineered stone benchtop cutting is a newer source of accelerated silicosis in NZ).

3. Biological hazards: pathogens encountered in healthcare (needlestick injuries: HIV, Hep B, Hep C transmission risk), farming (leptospirosis from cattle/deer urine), laboratory work, and abattoirs.

4. Psychosocial hazards: job strain (high demand, low control), bullying and harassment, shift work (disrupts circadian rhythm; associated with CVD, T2DM, cancer), workplace violence. These are recognised as significant occupational health hazards by WorkSafe NZ.

WorkSafe New Zealand: the workplace health and safety regulator established under the Health and Safety at Work Act 2015 (HSWA). The HSWA implemented recommendations from the Royal Commission into the Pike River Mine Disaster (2010), which killed 29 men. The HSWA imposes primary duties on PCBUs (Persons Conducting a Business or Undertaking) to ensure the health and safety of workers, so far as is reasonably practicable.

ACC and occupational injury: ACC covers work accidents and schedules of occupational diseases. NZ's fatal injury rate has declined significantly since HSWA implementation. Agriculture, construction, and forestry remain the highest-risk industries.

Climate Change and Health

The WHO and Lancet Commission on Health and Climate Change identify climate change as the "biggest global health threat of the 21st century." Its health impacts are mediated through multiple pathways:

Direct effects:

• Extreme heat events: heat stroke, cardiovascular events, exacerbation of chronic disease. The elderly, outdoor workers, and those in urban "heat islands" are most vulnerable. Heat mortality will increase significantly without mitigation.
• Extreme weather events: flooding (drowning, injury, displacement, contaminated water supplies), cyclones, droughts (food insecurity, suicide risk in farming communities).

Indirect effects:

• Vector-borne disease range expansion: warmer temperatures expand the geographic range of disease vectors. Of relevance to NZ: dengue fever is currently not endemic but the mosquito vectors (Aedes aegypti, Aedes albopictus) could establish if temperatures rise and if introduced. Ross River virus and Barmah Forest virus (Australia) are risks. Globally, malaria and dengue ranges are expanding.
• Food security: disrupted agriculture from drought, flooding, and extreme weather threatens global food supply. Nutritional diseases may increase.
• Mental health: eco-anxiety, grief related to environmental loss, and climate-related displacement cause significant mental health burden.
• Air quality: wildfire smoke (PM2.5) increases with climate change; more frequent and intense fires in Australia affect NZ air quality.

NZ-specific climate health risks: coastal flooding (Pacific communities, low-lying areas), agricultural disruption (drought in Hawke's Bay, Canterbury), increased flooding events (Cyclone Gabrielle 2023 — 11 deaths; widespread farm and infrastructure damage in Hawke's Bay and Northland), and mental health impacts in rural/farming communities.

NZ climate policy: the Zero Carbon Act (Climate Change Response (Zero Carbon) Amendment Act 2019) sets binding targets for net-zero long-lived greenhouse gases by 2050 and biogenic methane reduction targets for the agricultural sector. The Climate Change Commission (He Pou a Rangi) provides independent advice.