Exposure Toxicology

The study of toxicological effects of gases and particles on living cells is well established, with in-vitro techniques often used as a complement to in-vivo studies.

In-vitro exposure work typically uses a flow of gas / aerosol, running this over cells which are themselves at an air/liquid interface. This allows direct exposure of the cells to the material of interest, although precise measurement of dosage remains challenging under some circumstances, and particularly so for aerosol particles.

Aerosol exposure and size characterisation

The deposition of the aerosol onto cells will vary with the size of the particles. To understand both exposure and dosage, an understanding of the particle size distribution (which may vary with time) is advantageous.

Representative exposure

In mammals, mechanisms exist to remove large (>1 micron) particles in the upper airways, such that the deep lung cells are exposed only to smaller particles.

In-vitro exposure to aerosols typically does not feature this size cutoff, meaning that cells in such tests may be exposed to elements of an aerosol which is not representative of in-vivo. Further, the use of mass as a preferred metric for dosage means that larger particles (with much greater mass per particle) dominate.

It is therefore desirable to size select, allowing only particles smaller than a user-chosen threshold to reach the cells. This size selection should not involve a requirement for vacuum or temperature extremes, to avoid subjecting the cells downstream to harmful and non-representative conditions.

Size dependent exposure selection

Both delivered dose and toxic effects may vary with particle size.

It's desirable to be able to select particles within a narrow size range for exposure tests, to permit investigation of possible effects.

Aerosol physical characterisation

The behaviour of aerosols in the lungs, including deposition sites and efficiency, is governed by aerodynamic diameter. For spherical particles, the relationship between aerodynamic diameter, and particle mass is easily understood.

However, many solid aerosol particles are not spherical, for example soot agglomerates, engineered nanoparticles and many minerals. In this case, a detailed understanding of the physical properties of the aerosol is essential to understand and accurately model behaviour.

Cambustion instruments and techniques for aerosol toxicology

Cambustion offer a range of instruments to assist with the above challenges and offer exciting opportunities in aerosol toxicology.