HYDROGEN SULFIDE LIMITS: HEALTH, ODOR, OR WELFARE BASED?

This paper discusses hydrogen sulfide limits for various states that have recently updated their limits or whose limits demonstrate a distinction between health and odor-based limits. Odor discussions often focus on hydrogen sulfide because it has a low odor threshold and it is easily detected and recognized. There is a widely held public opinion that if odors are apparent, whether from wastewater processes, landfill gas emissions, or other sources, that these odors are a health concern. The differences between health and welfare/nuisance concerns and how emission limits are established is presented. Although some states base their emission limits on health concerns and some base the limits on welfare concerns, from the public's perspective both types of limits are often considered to be health-based.As an example, both California and New Jersey have the same acute (1-hour) hydrogen sulfide guideline of 30 parts per billion by volume (ppbv). However, California refers to the guideline as being welfare-based and New Jersey refers to the guideline as healthbased. The implications of these and similar distinctions are discussed. The discussion also focuses on whether the limits are guidelines or standards and what impact this has on community odor concerns. The public health concerns are discussed along with the broader potential impact these concerns are having on changing public policy topics, such as newly proposed hydrogen sulfide limits that were recently enacted in North Carolina and under debate in Massachusetts.Laboratory and field monitoring limitations are discussed, along with possible odor assessment approaches relative to defining health implications. The differences between guidelines and standards and how these limits are derived are presented. Odor detention thresholds for common wastewater emissions are discussed, along with comparisons of these odor thresholds to worker exposure thresholds and the range of individual state ambient health thresholds. This comparison demonstrates that odor thresholds are significantly lower than health thresholds and, therefore, that odor cannot immediately translate to health concerns; the public policy implications of these are presented.