Guidance on health risks in cannabis grow houses


Purpose

This Department of Health guidance is to alert local government authorities to the public health risks associated with cannabis grow houses and how these risks may be managed.

The information is provided as guidance only, as it is at the discretion of local government authorities as to what action, if any, they take

Occurrence and Risks 

The Western Australian Police Force has detected and closed increasing numbers of residences where large crops of cannabis (marijuana) plants are being grown, often hydroponically. Organised crime syndicates are usually involved in this activity and may target private rental properties for the purpose. It is entirely illegal and has nothing to do with cannabis production for medicinal reasons.

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During their work in grow houses, police will remove the plants, any other illicit drugs, and equipment associated with the cultivation. Police will also contact Western Power to make safe any illegal power or wiring modifications to the home. While police make every effort to ensure that major physical hazards are removed or mitigated, it is not their role to address public health or structural safety issues in the building.

The most significant risks at these premises are associated with physical safety during entry or assessment of the property, often due to the structural stability of the house. This may relate to unauthorised alterations, including illegal and unsafe electrical modifications, removal of sections of walls or load bearing structural components, potential water damage and exposure to spores from mould infestation. Mould spores can be inhaled and may cause a range of respiratory and allergic (e.g. asthma) conditions in susceptible people. This is particularly so if there are any disturbing activities at the time, such as moving furniture or structural repairs.

Chemicals may also be used in cannabis cultivation, including pesticides, fertilisers (some phosphate-based) and concentrated nutrient mixes containing trace elements and a range of heavy metals. These chemicals may remain at the property as a residue on surfaces or within its atmosphere through volatilisation.

If cannabis or other illicit drugs, such as methylamphetamine, have been smoked in the premises, they may also remain there as residues.

Police reports

Currently, the police notify both the LGA and DoH of the closure of houses used for illicit cannabis cultivation.

The police cannabis grow house reports contain information about the extent and location of damage, as well as any significant identified hazards

Legislation

LGAs may take action on the owners of the grow house where a house is deemed to be unfit for habitation. Other building legislation related to structural safety or integrity may also apply.

Section 135 of the Health (Miscellaneous Provisions) Act 1911 provides that a local government may declare any house, or specified part of a house, to be unfit for human habitation and may direct that the house, or part of the house, shall not be inhabited or occupied by any person. Where such a declaration has been made by way of cleanliness or want of repair, the local government can issue a notice to the owner requiring them to clean or repair the house within a given time frame and in a manner specified in the notice. Where a person fails to comply with that notice, the local government may carry out the work specified in the notice and recover all expenses from the owner.

Notification and management process

Currently, DoH receives the police report and then contacts the relevant LGA by email and phone. The DoH does not have a role other than as a conduit and record-keeper of these notifications, and occasionally provision of chemical or mould-related advice.

The LGA has discretion on what action if any it may wish to take in relation to the grow house. This will be informed by the police report which outlines the character of the damage to the premises and associated hazards.

If the premises are visited by local government officers, it is important that they take precautions against possible hazards as indicated below.

Pre-entry

Normally this would include site report familiarisation, checking availability of appropriate personal protective equipment (PPE) and ensuring the electricity is off or safety checked.

The PPE should include:

  • A respirator with ‘organic vapour’ and particulate filter cartridges, or a minimum P2 carbon type dust mask;
  • A disposable suit; and
  • Gloves and robust boots.

Initial Entry Procedure 

Using PPE, an initial entry is made to make the site safe for the main inspection by way of ventilating the premises and identifying and highlighting any hazards. Ventilation is important if the building has been closed for an extended period of time and if mould is present.

Main Inspection

The premises are then surveyed with a view to taking action on its clean-up and repair. Any disturbing activities should be minimised. PPE should be as above for initial entry although the P2 mask may be all that is required for respiratory protection.

Repairing and cleaning up the residence may require experienced trades professionals and also licensed building inspectors and certifiers. In the case of extensive mould growth, a specialist cleaner (PDF 76KB) may be necessary.

Further related information is available at

For further advice, please contact

Environmental Health Directorate
Phone (08) 9222 2000
Email ehinfo@health.wa.gov.au