## 1 Introduction  
The anthrax attacks of 2001 showcased the non-traditional attempts by which individuals or extremist groups can attempt to cause harm to the United States or other countries around the world. These events led to an increase in defense research and mitigation protocols for biological and toxin contamination which were either non-existent or immature in their development at the time. Surface sampling of biological agents was, and still is, an area of focus that has received significant attention as a result of the 2001 anthrax letters. However, relative to the published data available for surface sampling of biological warfare agents, very little focus has been directed to surface sampling studies of dusty agents, small molecules attached to an aerosolized carrier, and biologically derived toxins such as ricin. This lack of attention is evidenced by a single published report on surface sampling of a ricin-like compound since the 2001 attacks [1]. Ricin is one of the most toxic naturally occurring compounds on Earth with amounts as low as 500 \(\upmu\)g being lethal to a human adult. Currently, there is no proven treatment for individuals poisoned by this toxin [2]. The protein resides naturally in the castor bean and accounts for approximately 1%-5% of the bean's total mass [3,4]. Despite the availability and potential use by terrorists, there is little peer-reviewed literature reporting surface sampling data of native ricin. This lack of available information and research is likely due to the toxic nature and subsequent health risk for researchers. In addition to the toxicity of the native protein, a suspected reason for the lack of published toxin surface sampling data is the inherent difficulty in finding suitable non-toxic simulants. While there are many non-pathogenic organisms within the _Bacillus_ genus which are commonly used as _B. anthracis_ Ames simulants such as _Bacillus thuringiensis_, _Bacillus atrophaeus_, and _Bacillus subtilis_, as well as non-pathogenic _Bacillus anthracis_ strains such as _Ba_ sterne and _Ba_ delta sterne, until recently the sampling community has been lacking a non-toxic molecule of close homology to ricin to perform sampling studies. Historically, plant oils, egg white albumen, and other ricin-like plant proteins have been utilized as a non-toxic substitute for toxins and dusty agents. Unfortunately, all of these materials have inherent characteristics and properties such as sticking to equipment and not being recognized by antibodies used in ricin assays thus making them poor simulants for the ricin molecule. Recently, a recombinant non-toxic ricin has become commercially available which overcomes the previous ricin simulant challenges. This protein contains both the A and B ricin subunits which are covalently bonded together significantly decreasing the toxicity of the molecule by rendering the protein incapable of entering the cell. Additionally, a point mutation at the active site of the A subunit ensures that in the unlikely event that the A subunit is able to enter the cell, the molecule will be unable to properly bind to rRNA and inhibit protein synthesis, the mechanism of toxicity of ricin, further ensuring non-toxic characteristics. Additionally, the recombinant ricin used in this study is recognized by commercially available ricin antibodies currently used to detect ricin in biodefense environmental samples at sensitivity levels equivalent to that of native ricin. Our study evaluates four commercial off the shelf (COTS) swab materials, cotton, rayon, polyurethane (Dacron), and a polyurethane macrofoam, traditionally used in sampling studies, for the ability to recover both liquid deposited and a dry aerosol deposition of recombinant ricin from glass, polycarbonate, vinyl tile, and Chemical Agent Resistant Coating (CARC) painted steel coupons.