Skip to main content.

Appendix 1: How Environmental and Tolerable Exposure Limits are Set

Exposure limits for hazardous substances may be set by ERMA under the HSNO Act and regulations to protect the general public and the environment. [HSNO also provides for the setting of "workplace exposure standards" to ensure worker safety. These have been excluded from the discussion because no significant compliance and enforcement problems have arisen.] They are enforceable controls, applied to new substances when they are approved under Part V of the Act and to existing substances when they are transferred to the Act.

The www.ermanz.govt.nz website provides access to the EELs that have been set by ERMA. However, these are listed as components of a substance and it is not always clear what compound/product the EEL relates to. For example, the website lists an EEL for copper, but it is not clear that this EEL applies only to copper in specific new, approved substances, not to all sources of copper. This was not the intention for EELs when the HSNO policy was originally drafted. (In this document, we suggest the limit for copper should be set in a RMA site-specific context.)

Figure 5.1: Environmental exposure limit development process

Thumbnail of image. See figure at its full size (including text description).

TELs are controls set by ERMA to manage the risks posed by toxic substances to human health. Single-value concentration limits are set for exposure sources to humans (eg, air, water, soil, surface deposition). TELs are derived from potential daily exposure (PDE) values, which in turn are derived from acceptable daily exposure (ADE) or reference dose (RfD) values. The process for setting TELs is described in the Hazardous Substances (Classes 6, 8, and 9 Controls) Regulations 2001. In general, TELs follow a weight of evidence approach and are a means to protect the general population from involuntary exposure and accidental exposure (eg, a child ingesting a crayon).

An example of how TELs can be used is in agricultural spray modelling. If an applicator has the technology available to them, they can input the TEL into their model, along with current weather conditions (wind speed, wind direction, temperature) and come up with required buffer zones to ensure that the TEL is not exceeded at the property boundary.

Figure 5.2: Tolerable exposure limit development process

Thumbnail of image. See figure at its full size (including text description).

Please note: TELs do not currently cover non-food source ingestion. Amendments have been proposed to the Hazardous Substances (Classes 6, 8, and 9) Controls Regulations 2001 to allow TELs to be set for non-food sources. This will result in protection of the general public from exposure to non-food source poisoning (eg, ingestion of soil or dust).


[ Previous | Next ]