2026 Rankings

EPA Radon Zone 1 ZIP Codes in Maryland - 2026

Last updated: August 31, 2026

277 ZIP codes ranked by Radon Zone #1: ZIP 21001 (Aberdeen, MD) - Zone 1 (highest potential)
Lead Violations Lowest Score Safest Flood Risk Energy Cost Radon PFAS Reliability EJ Index Homebuyer Risk CO & Gas Safest Gas Remediation Burden Unresolved Violations (by Utility) Water Equity (by Utility)

Out of 277 ZIP codes with data in Maryland, these are the lowest-ranked areas for radon zone. See also: National ZIP Codes in EPA Radon Zone 1 | All Maryland Rankings

Statistic Value
ZIP codes ranked 277
Lowest value Zone 1 (highest potential)
Median value Zone 1 (highest potential)
State Maryland

100 Lowest-Ranked ZIP Codes

Rank ZIP Code City State Radon Zone Safety Score
1 21001 Aberdeen MD Zone 1 (highest potential) 48/100
2 21042 Ellicott City MD Zone 1 (highest potential) 48/100
3 21771 Mount Airy MD Zone 1 (highest potential) 48/100
4 21788 Thurmont MD Zone 1 (highest potential) 48/100
5 21005 Aberdeen Proving Ground MD Zone 1 (highest potential) 49/100
6 21014 Bel Air MD Zone 1 (highest potential) 49/100
7 21015 Bel Air MD Zone 1 (highest potential) 49/100
8 21157 Westminster MD Zone 1 (highest potential) 49/100
9 21703 Frederick MD Zone 1 (highest potential) 49/100
10 21769 Middletown MD Zone 1 (highest potential) 49/100
11 20837 Poolesville MD Zone 1 (highest potential) 50/100
12 21074 Hampstead MD Zone 1 (highest potential) 50/100
13 21102 Manchester MD Zone 1 (highest potential) 50/100
14 21713 Boonsboro MD Zone 1 (highest potential) 50/100
15 21756 Keedysville MD Zone 1 (highest potential) 50/100
16 21787 Taneytown MD Zone 1 (highest potential) 50/100
17 21078 Havre De Grace MD Zone 1 (highest potential) 59/100
18 21229 Baltimore MD Zone 1 (highest potential) 60/100
19 20850 Rockville MD Zone 1 (highest potential) 61/100
20 20851 Rockville MD Zone 1 (highest potential) 61/100
21 20852 Rockville MD Zone 1 (highest potential) 61/100
22 20853 Rockville MD Zone 1 (highest potential) 61/100
23 20854 Potomac MD Zone 1 (highest potential) 61/100
24 20855 Derwood MD Zone 1 (highest potential) 61/100
25 21210 Baltimore MD Zone 1 (highest potential) 62/100
26 21211 Baltimore MD Zone 1 (highest potential) 62/100
27 20794 Jessup MD Zone 1 (highest potential) 63/100
28 21043 Ellicott City MD Zone 1 (highest potential) 63/100
29 21163 Woodstock MD Zone 1 (highest potential) 63/100
30 21784 Sykesville MD Zone 1 (highest potential) 63/100
31 21071 Glyndon MD Zone 1 (highest potential) 64/100
32 21117 Owings Mills MD Zone 1 (highest potential) 64/100
33 21136 Reisterstown MD Zone 1 (highest potential) 64/100
34 21201 Baltimore MD Zone 1 (highest potential) 64/100
35 21202 Baltimore MD Zone 1 (highest potential) 64/100
36 21205 Baltimore MD Zone 1 (highest potential) 64/100
37 21206 Baltimore MD Zone 1 (highest potential) 64/100
38 21209 Baltimore MD Zone 1 (highest potential) 64/100
39 21212 Baltimore MD Zone 1 (highest potential) 64/100
40 21213 Baltimore MD Zone 1 (highest potential) 64/100
41 21214 Baltimore MD Zone 1 (highest potential) 64/100
42 21215 Baltimore MD Zone 1 (highest potential) 64/100
43 21216 Baltimore MD Zone 1 (highest potential) 64/100
44 21217 Baltimore MD Zone 1 (highest potential) 64/100
45 21218 Baltimore MD Zone 1 (highest potential) 64/100
46 21223 Baltimore MD Zone 1 (highest potential) 64/100
47 21224 Baltimore MD Zone 1 (highest potential) 64/100
48 21230 Baltimore MD Zone 1 (highest potential) 64/100
49 21231 Baltimore MD Zone 1 (highest potential) 64/100
50 21233 Baltimore MD Zone 1 (highest potential) 64/100
51 21239 Baltimore MD Zone 1 (highest potential) 64/100
52 21250 Baltimore MD Zone 1 (highest potential) 64/100
53 21251 Baltimore MD Zone 1 (highest potential) 64/100
54 21287 Baltimore MD Zone 1 (highest potential) 64/100
55 21740 Hagerstown MD Zone 1 (highest potential) 64/100
56 21793 Walkersville MD Zone 1 (highest potential) 64/100
57 20732 Chesapeake Beach MD Zone 1 (highest potential) 65/100
58 21702 Frederick MD Zone 1 (highest potential) 65/100
59 21795 Williamsport MD Zone 1 (highest potential) 65/100
60 20657 Lusby MD Zone 1 (highest potential) 66/100
61 20678 Prince Frederick MD Zone 1 (highest potential) 66/100
62 20723 Laurel MD Zone 1 (highest potential) 66/100
63 21009 Abingdon MD Zone 1 (highest potential) 66/100
64 21017 Belcamp MD Zone 1 (highest potential) 66/100
65 21040 Edgewood MD Zone 1 (highest potential) 66/100
66 21045 Columbia MD Zone 1 (highest potential) 66/100
67 21046 Columbia MD Zone 1 (highest potential) 66/100
68 21085 Joppa MD Zone 1 (highest potential) 66/100
69 21104 Marriottsville MD Zone 1 (highest potential) 66/100
70 21130 Perryman MD Zone 1 (highest potential) 66/100
71 21701 Frederick MD Zone 1 (highest potential) 66/100
72 21704 Frederick MD Zone 1 (highest potential) 66/100
73 21710 Adamstown MD Zone 1 (highest potential) 66/100
74 21716 Brunswick MD Zone 1 (highest potential) 66/100
75 21750 Hancock MD Zone 1 (highest potential) 66/100
76 21754 Ijamsville MD Zone 1 (highest potential) 66/100
77 21770 Monrovia MD Zone 1 (highest potential) 66/100
78 21774 New Market MD Zone 1 (highest potential) 66/100
79 21777 Point Of Rocks MD Zone 1 (highest potential) 66/100
80 21783 Smithsburg MD Zone 1 (highest potential) 66/100
81 20629 Dowell MD Zone 1 (highest potential) 67/100
82 20688 Solomons MD Zone 1 (highest potential) 67/100
83 20812 Glen Echo MD Zone 1 (highest potential) 67/100
84 20814 Bethesda MD Zone 1 (highest potential) 67/100
85 20815 Chevy Chase MD Zone 1 (highest potential) 67/100
86 20816 Bethesda MD Zone 1 (highest potential) 67/100
87 20817 Bethesda MD Zone 1 (highest potential) 67/100
88 20818 Cabin John MD Zone 1 (highest potential) 67/100
89 20832 Olney MD Zone 1 (highest potential) 67/100
90 20833 Brookeville MD Zone 1 (highest potential) 67/100
91 20860 Sandy Spring MD Zone 1 (highest potential) 67/100
92 20861 Ashton MD Zone 1 (highest potential) 67/100
93 20866 Burtonsville MD Zone 1 (highest potential) 67/100
94 20868 Spencerville MD Zone 1 (highest potential) 67/100
95 20871 Clarksburg MD Zone 1 (highest potential) 67/100
96 20874 Germantown MD Zone 1 (highest potential) 67/100
97 20876 Germantown MD Zone 1 (highest potential) 67/100
98 20877 Gaithersburg MD Zone 1 (highest potential) 67/100
99 20878 Gaithersburg MD Zone 1 (highest potential) 67/100
100 20879 Gaithersburg MD Zone 1 (highest potential) 67/100

Methodology

This ranking is limited to EPA county-level radon zone classification. Zone 1 identifies the highest county-level potential category; it does not measure a home or establish whether any building is above an action level. Within Zone 1, ZIP codes are sub-ranked by Home Safety Score to organize area context.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-08-31.

Frequently Asked Questions

What is EPA Radon Zone 1?

Zone 1 is the EPA highest county-level radon-potential category. It is not a measurement for a home and cannot determine whether a building is above an action level. A home test is required for that decision.

Should I test for radon?

The EPA recommends testing all homes regardless of radon zone. A DIY test kit costs $15-40. Professional testing costs $150-250. If levels exceed 4 pCi/L, mitigation systems ($800-2,500) can reduce radon by up to 99%.

Explore More Rankings

How this ranking is calculated, data sources, and limitations: Rankings Methodology →

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Disclaimer: Rankings are based on EPA, FEMA, and federal agency data. They reflect historical patterns and risk indicators, not necessarily current conditions. For the most current information, contact your local water utility or request a Consumer Confidence Report.

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