EQUATIONS FOR CALCULATION OF HRVs FOR NONCARCINOGENIC EFFECTS OF TOXICANTS

Subpart 1. Scope. This part establishes the method for determining the health risk values (HRVs) for noncarcinogenic effects of toxicants. Subp. 2. General equation; calculating HRV for noncarcinogenic effect of toxicant. The equation for calculating an HRV for a noncarcinogenic effect of a toxicant is: HRV = NOAEL [ADJ] or LOAEL [ADJ] or BMC [ADJ] ----------------------------------------------------- (Uncertainty factor)(Modifying factor) × 1,000 or HRV = NOAEL [HEC] or LOAEL [HEC] or BMC [HEC] ----------------------------------------------------- (Uncertainty factor)(Modifying factor) × 1,000 Where: A. HRV is expressed in units of micrograms per cubic meter (µg/m 3 ) of air; B. NOAEL [ADJ] or [HEC] , LOAEL [ADJ] or [HEC] , or BMC [ADJ] or [HEC] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; C. uncertainty factor and modifying factor are unitless; D. the default value for modifying factor is one unless otherwise specified in part 4717.8100 or 4717.8150 ; and E. 1,000 is a factor to convert milligrams to micrograms. Subp. 3. Equation for NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] ; particles with respiratory effect. The equation for calculating a NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] for a particle having a respiratory effect is: NOAEL [HEC] or LOAEL [HEC] or BMC [HEC] = NOAEL [ADJ] or LOAEL [ADJ] or BMC [ADJ] × RDDR Where: A. NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; B. NOAEL [ADJ] , LOAEL [ADJ] , or BMC [ADJ] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; and C. RDDR is the regional deposited dose ratio and is unitless. Subp. 4. Equation for NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] ; particles with extrarespiratory effect. The equation for calculating a NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] for particles with an extrarespiratory effect is: NOAEL [HEC] or LOAEL [HEC] or BMC [HEC] = NOAEL [ADJ] or LOAEL [ADJ] or BMC [ADJ] × RDDR ER Where: A. NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; B. NOAEL [ADJ] , LOAEL [ADJ] , or BMC [ADJ] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; and C. RDDR ER is the regional deposited dose ratio for extrarespiratory effects and is unitless. Subp. 5. Equation for NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] ; gas with respiratory effect. The equation for calculating the NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] for a gas having a respiratory effect is: NOAEL [HEC] or LOAEL [HEC] or BMC [HEC] = NOAEL [ADJ] or LOAEL [ADJ] or BMC [ADJ] × RGDR Where: A. NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; B. NOAEL [ADJ] , LOAEL [ADJ] , or BMC [ADJ] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; and C. RGDR is the regional gas dose ratio in the specific region of the respiratory tract and is unitless. Subp. 6. Equation for NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] ; gas with extrarespiratory effect. The equation for calculating the NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] for a gas having an extrarespiratory effect is: (H b/g ) A NOAEL [HEC] = NOAEL [ADJ] × ----------- (H b/g ) H or (H b/g ) A LOAEL [HEC] = LOAEL [ADJ] × ----------- (H b/g ) H or (H b/g ) A BMC [HEC] = BMC [ADJ] × ----------- (H b/g ) H Where: A. NOAEL [HEC] , LOAEL [HEC] , or BMC [HEC] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; B. NOAEL [ADJ] , LOAEL [ADJ] , or BMC [ADJ] is expressed in units of milligrams per cubic meter (mg/m 3 ) of air; and C. (H b/g ) A /(H b/g ) H is the ratio of the blood:gas (air) partition coefficient of the chemical in the experimental animal to the blood:gas (air) partition coefficient of the chemical in a human; the ratio is unitless. If (H b/g ) A > (H b/g ) H or if the partition coefficient values are unknown, (H b/g ) A /(H b/g ) H = 1.0.