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Appendix C - Cancer. Risk .Assessment Calculation <br />Health assessors use a process called risk assessment to evaluate:potential effects. of chemicals on <br />health.. Risk:assessments use the..best available scientific information, as well as.profess!anaI judgement. <br />and policy, to estimate risks in a: consistent, standardized manner that is useful for decision making <br />about rna.riaging risks. The paragraphs below describe the process M D H used to estimate cancer risk for <br />a hypothetical, highly exposed resident of the area.near the Water Gremlin facility. Many of the inputs <br />and processes M D H uses are adopted from widely followed guidance from the. U.S. EPA (U.S. EPA, 2021). <br />In 2011, EPA derived an inhalation unit risk (IU.R) for TCE of 4..1E-06 (µg/m3)-T for three cancer types <br />combined -by using the measured increase in human kidney cancer risk and adjusting for potential <br />increased risk.of non_Hodgkin's lymphoma and. liver: cancer (EPA; 2011). An IUR.isa.n estimate of the <br />increased cancer risk from inhalation.exposure to a concentration of 1 µg/m3 of a substance for a <br />lifetime. For risk.assessment purposes, this means an estimated 4.1 cases of cancer might occur due. to <br />this exposure if a million people -consistently breathe air.containing one. microgram of TCE per cubic <br />meter of air for70 years. <br />The EPA also recommends combining cancer IURs with age -dependent adjustment factors (ADAFs) to <br />account for greater early -life susceptibility for chemicals.that cause cancer by a mutation, whenever the <br />toxicity values are calculated from studies that only involve exposures in adults. EPA developed ADAFs of. <br />10,.3, a.nd 1 for application to the age groups of 0-2 years, 2-16 years, and 16-70 years; respectively <br />(EPA, 2005). For TCE, EPA recommends applying ADAFs only to the kidney cancer portion of the total <br />cancer risk estimate, because only that tumor type had sufficient evidence to conclude that TCE induces <br />cancer through a mutation (EPA, 2011). However,as'shown in the' calculation below, MDH takes an even <br />more protective a pp roach. by. applying ADAFs to the full inhalation unit risk; not.just the k.iidney cancer <br />portion. <br />To estimate community health.ris.ks, risk assessors often calculate risk for what. is: called a "reasonable <br />maximurt exposure" (RME) scenario.. For the purpose. of assess!hg exposure to TCE. in air surrounding <br />the Water Gremlin facility; the RME scenario is: considered to last from birth to 27 years (the. amount: of <br />time. Water Gremlin is thought.to have released TCE into the air; 199272018). The RM.E scenario also <br />uses an exposure point concentration (EPC) of 34 µg/m3 to represent an amount.of TCE in the air that <br />people breathed in this scenario; The EPC was calculated: by averaging the WE concentrations predicted <br />at the highest residential location frorn.2009'through '2018 (as indicated on the. maps in Appendix 6). <br />The cancer risk calculation is shown below for the RME.scenario assumptions described above. The <br />partial risk estimates -are derived by multiplying the IU.R by the age -specific ADAFs, the estimated EPC, <br />and exposure du.ration:adjustments (age group years divided by a.70 year lifetime. averaging time}.. The <br />lifetime risk of 1.5&04 is the sum of the partial risks: <br />Cancer Risk Calculation <br />r :�!Yr,-'.�h. YS� �"'-.Fs�j •� <br />Y',ri,-"1i.f.?�E'��'�;Y �;_nwi��: <br />��:�3= "«`'at�.c��.�..��•N� :� _ <br />r:� a'. "� �-y+fx <br />IN <br />.ra�� L � "k�w �j <br />�-' .!�. ��'���., <br />'u <br />fi .` 'k �v"f�I,>�.'��£=, "�r, S7ri-Ro-`}'' <br />�_r��T �i ..� �±,r, t1;2(r..,: fk�✓'�i' y�Y <br />�7Z }= .3 � lL ci.'.� Y`G. 3-.`'. .� �' '.�i�.:`'�' <br />---� C: �u�/_��� � <br />i• •lam. TS..u, .�:',"h w,' "' i <br />k <br />��) i ..F � ��5. <br />T. �'y.�, .Y a- <br />�3�stj+'►!j=�nt; <br />x F.r <br />- 6'� _ <br />'�t �+5�`�"i� s' <br />E.,; -�• ���aj.�� - �; <br />t>„�� �i�;- ] " � �-: ' .t <br />�,;y u�j� �y��r��y�? <br />��- t�� -• '4> <br />F, "-"� ;��.,��:�d . <br />L i'ti?�•�i �,;�- � S� SY'r•iY....�... <br />- ��; : , <br />� f� �G 2�'3�,'r ].� S �i`y�:i" <br />'�> >• SZ <br />0 to 2 years <br />4&50041 <br />10. 34 <br />2 years/70 years <br />3.98E=05 <br />2 to <16 years <br />0.0000041 <br />3 <br />� 34 <br />14 ye0rs/70 years <br />8.36E-05 I <br />16 to 27 years <br />0.0000041 <br />1.. <br />i 34 <br />11 yea rsno years <br />L21.19E-65 <br />Lifetime Risk <br />5E-04 <br />