Highest Radon Risk ZIP Codes in Maryland — 2026

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

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

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Radon Zone	Safety Score
1	21719	Cascade	MD	Zone 1 (High)	32/100
2	20859	Potomac	MD	Zone 1 (High)	33/100
3	20854	Potomac	MD	Zone 1 (High)	35/100
4	21122	Pasadena	MD	Zone 1 (High)	35/100
5	20610	Barstow	MD	Zone 1 (High)	40/100
6	20611	Bel Alton	MD	Zone 1 (High)	40/100
7	20617	Bryantown	MD	Zone 1 (High)	40/100
8	20629	Dowell	MD	Zone 1 (High)	40/100
9	20632	Faulkner	MD	Zone 1 (High)	40/100
10	20685	Saint Leonard	MD	Zone 1 (High)	40/100
11	20693	Welcome	MD	Zone 1 (High)	40/100
12	20704	Beltsville	MD	Zone 1 (High)	40/100
13	20733	Churchton	MD	Zone 1 (High)	40/100
14	20737	Riverdale	MD	Zone 1 (High)	40/100
15	20742	College Park	MD	Zone 1 (High)	40/100
16	20751	Deale	MD	Zone 1 (High)	40/100
17	20758	Friendship	MD	Zone 1 (High)	40/100
18	20768	Greenbelt	MD	Zone 1 (High)	40/100
19	20771	Greenbelt	MD	Zone 1 (High)	40/100
20	20782	Hyattsville	MD	Zone 1 (High)	40/100
21	20787	Hyattsville	MD	Zone 1 (High)	40/100
22	20788	Hyattsville	MD	Zone 1 (High)	40/100
23	20825	Chevy Chase	MD	Zone 1 (High)	40/100
24	20830	Olney	MD	Zone 1 (High)	40/100
25	20839	Beallsville	MD	Zone 1 (High)	40/100
26	20847	Rockville	MD	Zone 1 (High)	40/100
27	20848	Rockville	MD	Zone 1 (High)	40/100
28	20849	Rockville	MD	Zone 1 (High)	40/100
29	20857	Rockville	MD	Zone 1 (High)	40/100
30	20862	Brinklow	MD	Zone 1 (High)	40/100
31	20868	Spencerville	MD	Zone 1 (High)	40/100
32	20875	Germantown	MD	Zone 1 (High)	40/100
33	20880	Washington Grove	MD	Zone 1 (High)	40/100
34	20883	Gaithersburg	MD	Zone 1 (High)	40/100
35	20884	Gaithersburg	MD	Zone 1 (High)	40/100
36	20885	Gaithersburg	MD	Zone 1 (High)	40/100
37	20891	Kensington	MD	Zone 1 (High)	40/100
38	20897	Suburb Maryland Fac	MD	Zone 1 (High)	40/100
39	20898	Gaithersburg	MD	Zone 1 (High)	40/100
40	20899	Gaithersburg	MD	Zone 1 (High)	40/100
41	20913	Takoma Park	MD	Zone 1 (High)	40/100
42	21005	Aberdeen Proving Ground	MD	Zone 1 (High)	40/100
43	21010	Gunpowder	MD	Zone 1 (High)	40/100
44	21020	Boring	MD	Zone 1 (High)	40/100
45	21027	Chase	MD	Zone 1 (High)	40/100
46	21036	Dayton	MD	Zone 1 (High)	40/100
47	21085	Joppa	MD	Zone 1 (High)	40/100
48	21088	Lineboro	MD	Zone 1 (High)	40/100
49	21130	Perryman	MD	Zone 1 (High)	40/100
50	21150	Simpsonville	MD	Zone 1 (High)	40/100
51	21155	Upperco	MD	Zone 1 (High)	40/100
52	21156	Upper Falls	MD	Zone 1 (High)	40/100
53	21634	Fishing Creek	MD	Zone 1 (High)	40/100
54	21669	Taylors Island	MD	Zone 1 (High)	40/100
55	21715	Brownsville	MD	Zone 1 (High)	40/100
56	21718	Burkittsville	MD	Zone 1 (High)	40/100
57	21721	Chewsville	MD	Zone 1 (High)	40/100
58	21723	Cooksville	MD	Zone 1 (High)	40/100
59	21733	Fairplay	MD	Zone 1 (High)	40/100
60	21759	Ladiesburg	MD	Zone 1 (High)	40/100
61	21762	Libertytown	MD	Zone 1 (High)	40/100
62	21765	Lisbon	MD	Zone 1 (High)	40/100
63	21766	Little Orleans	MD	Zone 1 (High)	40/100
64	21767	Maugansville	MD	Zone 1 (High)	40/100
65	21770	Monrovia	MD	Zone 1 (High)	40/100
66	21775	New Midway	MD	Zone 1 (High)	40/100
67	21777	Point Of Rocks	MD	Zone 1 (High)	40/100
68	21778	Rocky Ridge	MD	Zone 1 (High)	40/100
69	21779	Rohrersville	MD	Zone 1 (High)	40/100
70	21781	Saint James	MD	Zone 1 (High)	40/100
71	21790	Tuscarora	MD	Zone 1 (High)	40/100
72	21794	West Friendship	MD	Zone 1 (High)	40/100
73	20612	Benedict	MD	Zone 1 (High)	45/100
74	20677	Port Tobacco	MD	Zone 1 (High)	45/100
75	20688	Solomons	MD	Zone 1 (High)	45/100
76	20695	White Plains	MD	Zone 1 (High)	45/100
77	20705	Beltsville	MD	Zone 1 (High)	45/100
78	20722	Brentwood	MD	Zone 1 (High)	45/100
79	20740	College Park	MD	Zone 1 (High)	45/100
80	20781	Hyattsville	MD	Zone 1 (High)	45/100
81	20783	Hyattsville	MD	Zone 1 (High)	45/100
82	20815	Chevy Chase	MD	Zone 1 (High)	45/100
83	20818	Cabin John	MD	Zone 1 (High)	45/100
84	20842	Dickerson	MD	Zone 1 (High)	45/100
85	20852	Rockville	MD	Zone 1 (High)	45/100
86	20853	Rockville	MD	Zone 1 (High)	45/100
87	20874	Germantown	MD	Zone 1 (High)	45/100
88	20878	Gaithersburg	MD	Zone 1 (High)	45/100
89	20895	Kensington	MD	Zone 1 (High)	45/100
90	21040	Edgewood	MD	Zone 1 (High)	45/100
91	21117	Owings Mills	MD	Zone 1 (High)	45/100
92	21722	Clear Spring	MD	Zone 1 (High)	45/100
93	21757	Keymar	MD	Zone 1 (High)	45/100
94	21758	Knoxville	MD	Zone 1 (High)	45/100
95	20639	Huntingtown	MD	Zone 1 (High)	50/100
96	20657	Lusby	MD	Zone 1 (High)	51/100
97	20714	North Beach	MD	Zone 1 (High)	51/100
98	20902	Silver Spring	MD	Zone 1 (High)	52/100
99	20906	Silver Spring	MD	Zone 1 (High)	52/100
100	20608	Aquasco	MD	Zone 1 (High)	53/100

Methodology

Radon rankings are based on EPA county-level radon zone classifications. Zone 1 (highest risk) has predicted average indoor radon levels above 4 pCi/L — the EPA action level. Zone 2 is moderate (2-4 pCi/L) and Zone 3 is low (below 2 pCi/L). Within Zone 1, ZIP codes are sub-ranked by Home Safety Score to prioritize areas with compounding risk factors.

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: 2026-06-04.

Frequently Asked Questions

What is EPA Radon Zone 1?

Zone 1 is the EPA highest-risk classification, meaning the county has predicted average indoor radon levels above 4 pCi/L — the level at which the EPA recommends mitigation. Radon causes about 21,000 lung cancer deaths per year in the U.S.

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%.